PORTLAND  CEMENT 


Published  by 

The   Chemical   Publishing   Co. 

Easton,  Penna. 

Publishers  of  Scientific  Books 

Engineering  Chemistry  Portland  Cement 

Agricultural  Chemistry  Qualitative  Analysis 

Household  Chemistry  Chemists'  Pocket  Manual 

Metallurgy,  Etc. 


PORTLAND  CEMENT 


Its  Composition,  Raw  Materials,  Manu- 
facture, Testing  and  Analysis 


BY 


RICHARD  K.  MEADE,  M.  S. 


GENERAL  MANAGER  OF  THE  TIDEWATER  PORTLAND    CEMENT 

CO.,    FORMERLY   CHEMIST   TO   THE   DEXTER   PORTLAND 

CEMENT    CO.,    THE    EDISON    PORTLAND   CEMENT 

CO.,  AND  THE  NORTHAMPTON  PORTLAND 

CEMENT     CO.,     AUTHOR     OF     THE 

CHEMISTS*  POCKET  MANUAL, 

ETC.,    ETC. 


SECOND  EDITION. 

EASTON.  PA. 

THE  CHEMICAL    PUBLISHING   CO. 
1911 


LONDON,   ENGLAND: 

WILLIAMS  &  NORGATE 

14  HENRIETTA  STREET,  COVENT  GARDEN,  W.  C. 


COPYRIGHT,  1911,  BY  EDWARD  HART. 


Mf 


PREFACE  TO  FIRST  EDITION. 


The  present  treatise  upon  Portland  cement  is  really  the  second 
edition  of  a  small  manual  by  the  writer,  published  some  four  years 
ago,  called  '  'The  Chemical  and  Physical  Examination  of  Portland 
Cement. ' '  In  preparing  this  new  edition,  it  seemed  wise  to  add  a 
section  on  the  manufacture  of  Portland  cement,  for  the  reason 
that  the  chemist  who  is  to  intelligently  supervise  the  process  of 
manufacture,  as  well  as  the  chemist  who  is  to  report  upon  the 
raw  materials  and  the  engineer  who  is  to  inspect  the  product, 
should  have  a  good,  general  knowledge  of  the  technology  of 
Portland  cement. 

It  was  also  found  necessary  to  rewrite  almost  the  entire  section 
upon  the  physical  testing  of  cement  in  order  to  give  special  promi- 
nence to  the  uniform  methods  of  testing  adopted  by  the  American 
Society  of  Civil  Engineers,  and  to  the  standard  specifications  of 
the  American  Society  for  Testing  Materials.  Much  new  matter 
has  also  been  added  to  the  section  on  the  analysis  of  cement  and 
its  raw  materials,  and  sections  on  the  experimental  manufacture 
of  small  lots  of  cement  and  on  the  history  of  the  industry  have 
been  included. 

The  analytical  methods  have  all  been  used  to  some  extent  in 
the  writer's  laboratory  and  have  been  found  satisfactory.  Com- 
ments as  to  their  accuracy  and  advice  as  to  the  best  methods  of 
manipulation  will  usually  be  found  with  each  method  under  the 
heading,  "notes." 

The  author  again  wishes  to  thank  the  many  friends  who  have 
aided  him  in  the  preparation  of  both  this  and  the  former  edition. 

NAZARETH,  PA.,  July,  1906. 


240777 


PREFACE  TO  THE  SECOND  EDITION. 


In  the  preparation  of  the  present  edition,  the  entire  text  of 
the  book  has  been  revised.  Much  new  matter  has  been  added, 
particularly  to  the  section  on  "Manufacture,"  which  has  been 
increased  by  76  pages.  Descriptions  of  the  newer  appliances  for 
the  Manufacture  of  Portland  Cement  have  been  added  so  that  it 
is  believed  that  this  section  represents  fairly  well  the  present 
state  of  the  industry  in  this  country. 

The  section  on  "Analytical  Methods"  has  been  somewhat  con- 
densed, so  far  as  space  goes,  by  the  printing  of  the  notes  in 
smaller  type  but  the  actual  matter  has  been  increased.  The 
section  on  "Physical  Testing"  has  been  revised  to  conform  to 
the  changes  made  in  the  standard  specifications  and  methods  of 
testing,  and  much  new  matter  has  been  included  here  also. 

A  chapter  has  been  added  to  the  book  on  the  "Investigation 
of  Materials  for  the  Manufacture  of  Portland  Cement".  The 
number  of  illustrations  has  been  increased  from  100  to  170  and 
among  the  new  ones  will  be  found  many  half-tones  showing  ac- 
tual installations  of  cement  machinery,  kilns,  etc. 

BALTIMORE,  MD.,  October,  1911. 


CONTENTS 


INTRODUCTION 

Chapter  I — Relation  Between  Mortar  Materials  and 
History  of  the  Development  of  the  American  Portland 
Cement  Industry 1-16 

Relation  Between  Portland  Cement  and  Other  Mortar 
Materials,  i;  The  Beginning  of  the  Cement  Industry 
in  England,  4;  Invention  of  Portland  Cement,  6;  Dis- 
covery of  Cement  Rock  in  the  United  States,  7;  Begin- 
ning of  the  Portland  Cement  Industry  in  the  United 
States,  10;  Development  in  Other  States,  u;  Produc- 
tion of  Portland  Cement  in  the  United  States,  13. 

Chapter  II — The  Nature  and  Composition  of  Portland 

Cement 17-42 

Composition  of  Portland  Cement,  17;  Le  Chatelier's 
Investigations,  18;  Newberry's  Formula,  20;  Torne- 
bohm's  Investigations,  20;  Richardson's  Work,  21; 
Researches  of  Day  and  Shepherd,  22;  Uncertainty  as 
to  Composition,  26;  Substances  Found  in  Cement,  28; 
Analyses  of  American  Portland  Cement,  29;  Lime,  30; 
Silica  and  Alumina,  33;  Ferric  Oxide,  34;  Magnesia, 
37;  Alkalies,  39;  Sulphur,  40;  Carbon  Dioxide  and 
Water,  41;  Other  Compounds  in  Portland  Cement,  42. 


MANUFACTURE 

Chapter  III— Raw  Materials 43-68 

Essential  Elements,  43;  Classification  of  Materials,  43; 
Limestone,  44;  Cement  Rock,  48;  Marl,  51;  Clay,  53; 
Shale,  54;  Analyses  of  Materials  Used  for  the  Manu- 
facture of  Portland  Cement  at  Various  Plants,  55; 
Blast  Furnace  Slag,  63;  Alkali  Waste,  64;  Gypsum,  65; 
Valuation  of  Raw  Materials,  66. 


VI  CONTENTS 

Chapter  IV — Proportioning  the  Raw  Materials 69-93 

Introduction,  69;  By  Using  the  Ratio  Between  Silicates 
and  Lime,  70;  By  Using  Newberry's  Formula,  72; 
Graphic  Method  for  Calculating  Cement  Mixture,  73; 
Fixed  Lime  Standard,  78;  Formulas  fora  Fixed  Lime 
Standard,  80;  Calculation  of  a  Three-Component  Mix, 
86;  Controlling  the  Mixture  in  the  Wet  Process,  88;  Cal- 
culating the  Probable  Analysis  of  Cement  Clinker,  91. 


Chapter  V — Quarrying,  Excavating,  Drying  and  Mix- 
ing the  Raw  Materials. 94-119 

Quarrying  Stone,  94;  Excavating  Marl,  98;  Mixing  the 
Raw  Materials,  101;  Storage  of  the  Raw  Materials,  103; 
Weighing  the  Raw  Materials,  106;  Dryers,  108;  Wet 
Process,  112;  Semi- wet  Process,  113;  Examples  of 
Treatment  of  Raw  Materials  at  Different  Mills,  115. 

Chapter  VI.  — Grinding  the  Raw  Materials  and  Grind- 
ing Machinery 120-159 

Introduction,  120;  Gyratory  Crusher,  121;  Pulverizing 
the  Raw  Materials,  1:4;  Crushing  Rolls,  124;  Pot 
Crusher,  125;  Hammer  Mill,  127;  Edge  Runner  Mill, 
129;  The  Ball  Mill,  130;  The  Kominuter,  135;  The 
Tube  Mill,  136;  Fuller-Lehigh  Mill,  142;  Griffin  Mill, 
145;  The  Huntington  Mill,  148;  Raymond  Roller  Mill, 
149;  Kent  and  Maxecon  Mills,  150;  Sturtevant  Ring- 
Roll  Mill,  151;  Newaygo  Separator,  151;  Air  Separa- 
tors, 152;  Capacity  of  Various  Grinders,  155;  Degree 
of  Fineness  of  the  Raw  Material,  156;  Conveyors,  158. 

Chapter  VII — Burning — Kilns  and  Process 160-199 

Shaft  Kilns,  160;  The  Rotary  Kiln,  166;  Mechanical 
Construction,  167;  Feeding  in  the  Raw  Materials,  170; 
Speed  of  Rotation,  171;  Kiln  Lining,  172;  Labor,  175; 
Capacity  and  Fuel  Consumption,  175;  Chemical 
Changes  Undergone  in  Burning,  176;  Temperature  of 
Burning,  184;  Degree  of  Burning,  187;  Thermo-Chem- 
istry  of  Burning,  188;  Excess  Air  Used  in  Burning,  195; 
Utilization  of  Waste  Heat,  197. 


CONTENTS  Vll 

Chapter  VIII— Burning    (Continued) — Fuel  and  Prep- 
aration of  the  Same 200-218 

Apparatus  for  Burning  Powdered  Coal,  200;  Coal,  204; 
Coal  Dryers,  205;  Pulverizing  the  Coal,  210;  Explosions, 
Storage  of  Coal,  Etc.,  213;  Burning  with  Natural  and 
Producer  Gas,  215. 

Chapter  IX — Cooling  and  Grinding  the  Clinker,  Stor- 
ing and  Packing  the  Cement,  Etc 219-251 

Cooling  the  Clinker,  219;  Adding  the  Retarder,  223; 
Grinding  the  Clinker,  224;  Stock  Houses,  226;  Pack- 
ing, 227;  Power  Plant,  232;  Complete  Equipment  of 
Plants,  236;  References  to  Descriptions  of  Plants,  245; 
Cost  of  Plant  and  Manufacture,  247. 


ANALYTICAL  METHODS 


Chapter  X — The  Analysis  of  Cement 252—304 

Preparation  of  the  Sample,  252;  Determination  of 
Siiica,  Ferric  Oxide  and  Alumina,  Lime  and  Magnesia, 
253;  Volumetric  Determination  of  Lime,  266;  Rapid 
Determination  of  Lime  Without  Separation  of  Silica, 
270;  Determination  of  Ferric  Oxide,  271;  Determina- 
tion of  Sulphuric  Acid,  280;  Determination  of  Total 
Sulphur,  283;  Determination  of  Sulphur  Present  as 
Calcium  Sulphide,  284;  Loss  on  Ignition,  287;  Determi- 
nation of  Carbon  Dioxide  and  Water,  288;  Determina- 
tion of  Carbon  Dioxide  Alone,  294;  Rapid  Determina- 
tion of  Carbon  Dioxide,  296:  Determination  of  Hygro- 
scopic Water,  298;  Determination  of  Alkalies,  300;  De- 
termination of  Phosphoric  Acid,  301;  Determination 
of  Manganese,  303;  Determination  of  Titanium,  303. 

Chapter  XI — The  Analysis  of  Cement  Mixtures 305-330 

Sampling,  305;  Rapid  Methods  for  Checking  the  Per- 
centage of  Calcium  Carbonate  in  Cement  Mixtures,  313; 
Determination  of  Silicates,  326;  Complete  Analysis  of 
Cement  Mixtures  or  Slurry,  327. 


yiii  CONTENTS 


Chapter  XII — Analysis  of  the  Raw  Materials 33I~347 

Methods  for  Limestone,  Cement  Rock,  and  Marl,  331; 
Methods  for  Clay  and  Shale,  338;  Methods  for  Gypsum 
or  Plaster  of  Paris,  345. 


PHYSICAL  TESTING 

Chapter  XIII— The  Inspection  of  Cement 348-360  . 

Standard  Specifications  for  Inspection,  348;  Methods  of 
Inspection,  349;  Inspection  at  the  Mill,  349;  Inspection 
on  the  Work,  352;  Standard  Methods  of  Sampling,  353; 
Samplers,  355;  Uniform  Specifications  and  Methods  of 
Testing,  358;  Tests  to  be  Made,  359. 

Chapter  XIV — Specific  Gravity 361-385 

Standard  Specifications  and  Method  of  Test,  361;  Notes 
on  the  Standard  Method,  363;  Other  Methods,  368;  With 
the  Schumann-Candlot  Apparatus,  368;  Jackson's  Ap- 
paratus, 369;  Simple  Apparatus  for  Specific  Gravity,  374; 
Meade's  Suspension  Method,  376;  Observations  on 
Specific  Gravity,  379;  Effect  of  Burning  on  the  Specific 
Gravity  of  Cement,  379;  Effect  of  Adulteration  on  the 
Specific  Gravity,  381;  Effect  of  Seasoning  Cement  or 
Clinker  on  Specific  Gravity,  382;  Specific  Gravity  upon 
Dried  and  Ignited  Samples,  383. 

Chapter  XV— Fineness 386-404 

Standard  Specification  and  Method  of  Test,  386;  Errors 
in  Sieves,  387;  Other  Methods,  388;  Methods  of  Siev- 
ing, Sieves,  Etc.,  388;  Determining  the  Flour  in  Cement, 
390;  Suspension  Method,39i;  Griffin-Goreham  Flourom- 
eter,  393;  Gary-Lindner  Apparatus,  395;  Observations 
on  Fineness,  396;  Effect  of  Fineness  on  the  Properties 
of  Portland  Cement,  396;  Influence  on  Color,  397;  In- 
fluence on  Soundness,  397;  Influence  on  Setting  Time, 
399;  Effect  of  Fineness  upon  Strength,  401;  Limitation 
of  the  Sieve  Test,  403. 


CONTENTS  IX 

Chapter  XVI— Time  of  Setting 405-425 

Standard  Specification  and  Method  of  Test,  405;  Nor- 
mal Consistency,  405;  Time  of  Setting,  406;  Notes, 
407;  Other  Methods,  409;  Observations  on  Setting 
Time,  413;  Factors  Influencing  the  Rate  of  Setting, 
•413;  Rise  in  Temperature  During  Setting,  415;  Influ- 
ence of  Sulphates  on  Setting  Properties,  416;  Influence 
of  Calcium  Chloride  on  Setting  Properties,  420;  Effect 
of  Storage  of  Portland  Cement  on  Its  Setting  Proper- 
ties, 421;  Influence  of  Slaked  Lime  on  Setting  Time, 
424;  Influence  of  Chemical  Composition  on  Setting 
Time,  425. 

Chapter  XVII— Tensile  Strength 426-455 

Standard  Specifications,  426;  Method  of  Operating  the 
Test,  426;  Standard  Sand,  426;  Form  of  Briquette,  426; 
Molds,  427;  Mixing,  428;  Molding,  428;  Storage  of 
Test  Pieces,  429;  Tensile  Strength,  430,  Notes,  430; 
Standard  Sand,  432;  Forms  of  Briquettes,  432,  Molds, 
433,  Mixing,  435;  Percentage  of  Water,  436;  Storage 
of  Briquettes,  437;  Testing  Machines,  439;  Rate  of 
Stress,  445;  Clips,  446;  Lack  of  Uniformity  in  Tensile 
Tests,  448;  Machines  for  Mixing  the  Mortar,  448; 
Machines  for  Molding  the  Briquettes,  450;  Observa- 
tions, 451;  High  Tensile  Strength  of  Unsound  Cements, 
451;  Relation  between  Neat  and  Sand  Strength,  452; 
Drop  in  Tensile  Strength,  453. 

Chapter  XVIII — Soundness 456-477 

Standard  Specification  and  Method  of  Test,  456;  Notes, 
458;  Other  Methods,  461;  German  Specifications,  461; 
Faija's  Test,  462;  Kiln  Test,  463;  Boiling  Test,  464; 
Calcium  Chloride  Test,  465;  Bauschinger's  Calipers, 
465;  Le  Chatelier's  Caliper's,  466;  White's  Microscopic 
Test  for  Free  Lime,  468;  Observations,  470;  Importance 
of  the  Test,  470;  Causes  of  Unsoundness,  470;  Effect  of 
Seasoning  on  Soundness,  471;  Effect  of  Fine  Grinding 
of  the  Raw  Materials  on  Soundness,  472;  Effect  of 
Sulphates  on  Soundness,  473;  Value  of  Accelerated 
Tests,  474. 


X  CONTENTS 

MISCELLANEOUS 

Chapter  XIX— The  Detection  of  Adulteration  in  Port- 
land Cement 478-484 

Tests  of  Drs.  R.  and  W.  Fresenius,  478;  Proposed  Tests, 
478;  Carrying  out  the  Tests,  480;  Le  Chatelier's  Test, 
481;  Preparation  of  the  Heavy  Liquid,  481;  Apparatus, 
482;  Test,  482;  Microscopic  Test,  483. 

Chapter  XX — The  Investigation  of  Materials  for  the 

Manufacturing  of  Portland  Cement 485-496 

Prospecting  Limestone  and  Cement-Rock  Deposits, 
485;  Clay  and  Shale,  489;  Marl,  490;  Trial  Burnings, 
491- 

Appendix — Tables 497-501 

Table  of  Atomic  Weights,  497;  Table  of  Factors,  497; 
Table  for  Converting  Mg2P2O7  to  MgO,  498;  Table  for 
Use  with  Permanganate  in  Lime  Determinations,  498; 
Table  Giving  Percentage  of  Water  for  Sand  Mixtures, 
501. 


INTRODUCTION. 


Chapter  I. 

RELATION  BETWEEN  MORTAR  MATERIALS  AND  HISTORY 

OF  THE  DEVELOPMENT  OF  THE  AMERICAN 

PORTLAND  CEMENT  INDUSTRY. 


Relation  Between  Portland  Cement  and  Other  Mortar  Materials. 
Mortar  materials  may  be  classified  according  to  their  proper- 
ties, methods  of  manufacture  and  materials  from  which  they  are 
made  as  follows: — 

1.  Common  Limes  are  made  by  burning  relatively  pure  lime- 
stone.    When  mixed  with  water  they  slake  and  show  no  hydrau- 
lic properties. 

2.  Hydraulic  Limes  are  made  by  burning  impure   limestone 
at  low  temperatures.    They  slake  with  water  but  show  hydraulic 
properties. 

3.  Natural  Cements  are  made  by  burning  impure  limestones 
at   a   low   temperature    (insufficient   to   vitrify).     They   do   not 
slake  with  water  but  require  to  be  ground  in  order  to  convert 
them  into  a  hydraulic  cement. 

4.  Portland   Cement   is   made   by   heating  to   incipient   vitri- 
faction  an  intimate  mixture  of  an  argillaceous  substance,  such 
as   clay  or   shale,   and  calcareous   substance,   such   as   limestone 
or  marl,  in  which  mixture  the  percentage  of  silica,  alumina  and 
iron  oxide  bear  to  the  percentage  of  lime  the  ratio  of  approxi- 
mately  i  :2,  which  vitrified  product  does  not  slake  with  water 
but  upon  grinding  forms  an  energetic  hydraulic  cement. 

5.  Puszolan  Cements  are  made  by  incorporating  slaked  lime 
with  finely  ground  slag  or  volcanic  ash  or  by  incorporating  a 
small  proportion  of  Portland  cement  clinker  with  suitably  treated 
slag  and  grinding  intimately  the  mixture. 


PORTLAND  CEMENT 


lfct  6.  Piasters:  ire  made  by  heating  gypsum  sufficiently  to  drive 


^b^f!  three-fourths*  "or   all  of  the  combined  water  which   it   con- 
tains" 'and*  grincfiri'if  finely  the  more  or  less  dehydrated  residue. 

Table  I  given  below  will  explain  the  above  classifications, 
while  tables  II  and  VII  show  the  composition  of  these  various 
materials. 


TABLE  I.—  SHOWING  THE  RELATION  BETWEEN  LIMES, 
CEMENTS  AND  PIASTERS. 


Raw 
materials 

Chemical 
treatment 

Mechanical 
treatment 

Hydraulic 
properties 

Classification 

Made  from  rel- 
atively pure 
limestones. 

Burned  at 
low  tem- 
peratures. 
600°  -i  200° 
C. 

Slake  on  addi- 
tion of  water 
to  burned 
product. 

Not     h  y  - 
draulic. 

i.  Common 
lime. 

Hydraulic. 

2.  Hydraul  i  c 
limes. 

Made  from  ar- 
gillaceous or 
impure  lime- 
stone. 

Do  not  slake  on 
addition  of 
water  but 
must  be 
ground  fine- 
ly for  use. 

3.  Natural 
Roma  n  or 
Rosendale 
cement. 

Made  from  an 
intimate 
mixture  of 
argillace  o  u  s 
and  calcar- 
eous sub- 
stances in 
proper  pro- 
portions. 

Burned   at 
high    tem- 
peratures. 
i3oo°-6ioo° 
C. 

4  .  For  1  1  a  n  d 
cement. 

Made  from 
mixtures  of 
slaked  lime 
and  blast- 
furnace  slag 
or  volca  n  i  c 
ash. 

Not  burned. 

5.  S  1  ag  or 
Puz  z  o  1  a  n 
cements. 

M  a  d  e*  f  r  o  m 
gypsum. 

Burned   at 
from  165- 

200°  C. 

Not      h  y  - 
draulic. 

6.  Plasters. 

MORTAR  MATERIALS  AND  CEMENT  INDUSTRY 


? 


4  PORTLAND  CEMENT 

History  of  the  Development  of  Mortar  Materials. 
When  lime  mortar  was  first  employed  or  what  people  dis- 
covered its  binding  properties  no  one  knows,  but  it  is  certain 
that  its  use  antedates  written  history.  It  has  been  found  be- 
tween the  stones  of  what  remains  of  a  very  ancient  temple  on 
the  Island  of  Cyprus,  supposed  to  be  the  oldest  ruin  in  the 
world.  The  Egyptians  used,  in  place  of  lime,  a  mortar  in  which 
partially  burned  gypsum  or  plaster  of  Paris  was  the  cementing 
factor  and  this  was  employed  in  the  construction  of  the  Pyr- 
amids, built  over  four  thousand  years  ago.  The  Romans  dis- 
covered that  a  mixture  of  lime  and  volcanic  ashes  would  harden 
under  water  and  hence  might  be  used  for  the  construction  of 
aqueducts,  cisterns,  docks,  etc.  They  used  this  mortar  in  many 
of  their  public  buildings  and  temples,  in  the  Pantheon,  in  the 
Baths  of  Caracalla  and  in  the  aqueduct  which  supplied  Rome 
with  water.  From  the  period  of  the  Romans,  no  advance  was 
made  in  the  technology  of  building  materials  until  the  latter 
part  of  the  eighteenth  century,  when  the  modern  cement  industry 
had  its  beginning. 

The  Beginning  of   the   Cement  Industry  in  England. 

The  cement  industry  proper  dates  from  the  researches  of  an 
English  engineer,  John  Smeaton,  who  had  been  employed  by  par- 
liament to  build  a  lighthouse  upon  a  group  of  gneiss  rocks,  in  the 
English  Channel,  just  off  the  coast  of  Cornwall.  These  crags, 
known  as  Eddystone,  were  at  high  tide  under  water  for  some 
hours  and  many  shipwrecks  had  occurred  upon  them.  They  were 
a  menace  to  the  navigation  of  this  part  of  the  channel  and  it  was 
necessary  to  warn  sailors  of  their  whereabouts.  Two  wooden 
structures  built  upon  them  had  been  subjected  to  the  fury  of  the 
elements  and  had  each  experienced  a  short  life. 

When  Smeaton  attacked  the  problem,  he  determined  to  build 
a  structure  which  would  weather  the  fiercest  storms  of  the  chan- 
nel and  would  come  out  of  these  an  enduring  monument  to  his 
engineering  skill.  One  of  the  greatest  difficulties  he  had  to  over- 
come was  the  failure  of  ordinary  lime  mortar  (the  discovery  of 


MORTAR  MATERIALS  AND  CEMENT   INDUSTRY  5 

which  dates  back  to  antiquity)  to  harden  under  water.  In  order 
that  his  foundations  should  be  firm,  it  was  necessary  that  some 
mortar  be  found  which  would  meet  this  difficulty.  To  this  end  he 
undertook  a  series  of  investigations  in  1756,  the  result  of  which 
was  the  discovery  that  the  hard,  white,  pure  limestones,  hitherto 
considered  best  for  lime  making,  were  in  reality  inferior  to  the 
soft  clayey  ones1;  for  from  these  latter  he  succeeded  in  obtain- 
ing a  lime  far  superior  to  any  then  in  use  because  it  not  only 
hardened  better  in  air,  but  would  also  harden  under  water.  Such 
a  limestone  Smeaton  found  near  at  hand,  at  Aberthaw,  in  Corn- 
wall, and  the  hydraulic  lime  formed  by  burning  this  stone  was  the 
basis  of  the  mortar  used  in  the  construction  of  the  Eddystone 
lighthouse. 

Smeaton  in  making  his  hydraulic  lime,  however,  used  only 
those  layers  of  his  quarry  which  after  burning  gave  a  product 
that  would  slake  with  water.  The  idea  of  burning  the  layers 
which  would  not  slake  readily  and  then  by  grinding,  convert  them 
into  a  very  energetic  hydraulic  lime  did  not  suggest  itself  to  him 
and  it  was  not  until  forty  years  later  that  this  first  improvement 
was  made  in  the  manufacture  of  hydraulic  lime.  In  1796,  one 
Joseph  Parker,  of  Northfleet,  in  Kent  Co.,  Eng.,  took  out  a  patent 
for  the  manufacture  of  a  hydraulic  lime  which  he  called  "Roman 
Cement"  and  which  he  made  by  calcining  or  burning  the  argillo- 
calcareous,  kidney-shaped  nodules  called  "septaria"  and  then 
grinding  the  resulting  product  to  a  powder.2  In  composition 
these  nodules  were  very  similar  to  what  we  now  call  Rosendale 
cement-rock.  They  occurred  geologically  in  the  London  clay 
formation  and  were  usually  obtained  from  the  shores  of  the  Isle 
of  Sheppy  where  they  were  washed  up  after  a  storm.  This 
cement  came  rapidly  into  favor  with  the  English  engineers  be- 
cause much  work  could  be  done  with  it  that  was  impossible  with 
quicklime.  In  1802  cement  was  produced  from  the  same  "sep- 
taria" at  Boulogne,  France,  and  this  was  the  beginning  of  the 
cement  industry  in  that  country. 

In   1810,   Edgar   Dobbs,   of   Southwick,   England,  obtained   a 

1  Smeaton— Narrative  of  the  building,  etc.,  of  the  Eddystone  Lighthouse,  Book  IV. 

2  Redgrave— Calcareous  Cements. 


6  PORTLAND 

patent  for  the  manufacture  of  an  artificial  Roman  cement  by  mix- 
ing carbonate  of  lime  and  clay,  in  suitable  proportions,  moisten- 
ing, molding  into  bricks,  and  burning  sufficiently  to  expel  the 
carbonic  acid,  without  vitrifying  the  mixture.  Soon  after  this, 
General  Sir  Wm.  Paisley,  in  England,  and  L.  J.  Vicat,  a  French 
engineer,  both  independently  of  each  other,  made  exhaustive  ex- 
periments looking  to  the  manufacture  of  an  artificial  Roman  ce- 
ment by  mixing  clay  with  chalk,  etc.  In  1813  Vicat  began  the 
manufacture  of  artificial  hydraulic  cement  in  France,  as  did  also 
James  Frost  in  England,  in  1822. 

Invention  of  Portland  Cement. 

In  1824,  Joseph  Aspdin,  a  bricklayer  of  Leeds,  England,  took 
out  a  patent  on  an  improved  cement  which  he  proposed  to  make 
from  the  dust  of  roads  repaired  with  limestone,  or  else  from  lime- 
stone itself  combined  with  clay,  by  burning  and  grinding.  This 
cement  he  called  "Portland  Cement,"  because  when  hardened  it 
produced  a  yellowish  gray  mass  resembling  in  appearance  the 
stone  from  the  famous  quarries  of  Portland,  England. 

Aspdin  is  usually  credited  with  the  invention  of  Portland  ce- 
ment and  while  he  certainly  did  originate  the  name  "Portland 
Cement"  he  probably  did  nothing  more  than  make  an  artificial 
Roman  cement,  which  had  been  done  before,  since  he  apparently 
did  not  carry  his  burning  to  the  point  of  incipient  vitrifaction, 
which  we  now  recognize  as  being  an  essential  point  in  the  manu- 
facture of  Portland  cement.1  Aspdin  erected  a  factory  at 
Wakefield,  England,  for  the  manufacture  of  his  cement,  which 
was  used  upon  the  Thames  Tunnel  in  1828.  At  first  Portland 
cement  was  sold  at  prices  considerably  lower  than  the  Natural 
or  Roman  Cement  of  Parker  and  his  successors,  and  it  was  not 
until  John  Grant,  in  1859,  decided  to  use  Portland  cement  in  the 
construction  of  the  London  drainage  canal,  of  which  he  was  chief 
engineer,  and  published  his  reasons  for  doing  so  in  the  transac- 
tions of  the  Institution  of  Civil  Engineers,  that  the  new  cement 
began  to  come  to  the  front. 

1  Michaelis — Thonindustrie  Zeitung,  Jan.  16,  1904. 


MORTAR  MATERIALS  AND  CEMENT  INDUSTRY  J 

It  is  evident  that  by  this  time  the  value  of  burning  the  clinker 
to  the  point  of  incipient  vitrifaction  had  been  discovered  and 
made  use  of — probably  first  in  the  famous  old  works  of  White  & 
Bros.,  established  by  James  Frost  at  Swanscombe,  in  1825,  and 
still  existent.  In  1852  the  first  German  Portland  cement  works 
were  established  near  Stettin.  The  Germans  were  quick  to  see 
the  value  of  the  new  building  material,  and  with  their  fine  tech- 
nologists soon  turned  out  a  better  product,  by  the  substitution  of 
scientific  methods  in  place  of  rules  of  thumb.  They  were  the  first 
to  appreciate  the  value  of  fine  grinding  of  the  cement,  and  until 
recently  the  German  Portlands  were  the  standards.  To-day  un- 
doubtedly the  best  Portland  cement  made  in  the  world  is  turned 
out  in  America. 

Discovery  of  Cement-Rock  in  the  United  States. 

In  this  country  the  cement  industry  began  with  the  discovery 
in  1818,  of  a  natural  cement -rock  near  Chittenango,  Madison  Co., 
N.  Y.,  by  Mr.  Canvass  White,  an  engineer  engaged  in  the  con- 
struction of  the  Erie  canal,  who  after  some  experimenting  ap- 
plied to  the  State  of  New  York  for  the  exclusive  right  to  manu- 
facture this  cement  for  twenty  years.  The  state  denied  his  re- 
quest but  gave  him  $20,000  in  recognition  of  his  valuable  discov- 
ery.1 His  cement  was  used  in  large  quantities  in  the  construc- 
tion of  the  Erie  canal  and  brought  a  price  of  about  twenty  cents 
a  bushel. 

As  the  greatest  users  of  cement  in  this  country  were  the  canals, 
and  as  they  at  that  time  furnished  the  only  means  for  the  trans- 
portation of  bulky  materials,  there  was  naturally  the  sharpest 
lookout  kept  along  their  line  of  construction  for  limestone  suit- 
able for  the  making  of  hydraulic  cement.  In  consequence  of  this, 
nearly  all  the  early  cement  mills  were  started  along  the  line  of, 
and  to  furnish  cement  for,  the  construction  of  some  canal.  In 
1825,  cement- rock  was  discovered  in  Ulster  County,  New  York, 
along  the  line  of  the  Delaware  and  Hudson  canal  and  in  the  fol- 
lowing year  a  mill  was  started  at  High  Falls  in  that  county.  In 
1828,  a  mill  was  built  at  Rosendale.  also  in  Ulster  County.  This 

1  Sylvester— History  of  Ulster  County,  N.  Y. 


8  PORTLAND  C£ME)NT 

soon  became  the  center  of  the  industry  and  the  cement  made  here 
was  called  Rosendale.  This  name  is  still  largely  applied  to  Ameri- 
can natural  cements.  The  first  cement  was  made  in  small  upright 
kilns.  Wood  was  used  as  fuel  and  the  burning  continued  for 
about  a  week.  The  clinker  was  then  ground  between  mill  stones 
by  water-power.  After  these  mills  had  been  in  operation  several 
years  continuous  kilns  were  introduced  which  permitted  the  clink- 
er to  be  drawn  daily,  coal  being  used  as  fuel. 

In  1829  cement-rock  was  discovered  near  Louisville,  Ky.,  while 
constructing  the  Louisville  &  Portland  Canal,  and  John  Hulme  & 
Co.  almost  immediately  began  the  manufacture  of  Louisville  ce- 
ment at  Shippingport,  a  suburb  of  Louisville.1 

During  the  construction  of  the  Chesapeake  and  Ohio  Canal, 
cement-rock  was  discovered,  in  1836,  in  Maryland,  at  Round  Top, 
near  Hancock,  and  it  has  been  manufactured  there  ever  since. 
Other  canals  along  whose  lines  cement-rock  was  discovered  with 
the  location  and  date,  are  the  Illinois  and  Michigan  Canal,  at 
Utica,  in  1838;  James  River  Canal,  at  Balcony  Falls,  Va.,  in 
1848;  and  Lehigh  Coal  and  Navigation  Co.  Canal,  at  Siegfried, 
Pa.,  in  1850.  At  all  of  these  points  the  manufacture  of  cement 
has  been  continuous.  Other  well  known  brands  of  cement  began 
to  be  manufactured  as  follows:  Akron,  N.  Y.,  1840;  Ft.  Scott, 
Kan.,  1868:  Buffalo,  N.  Y.,  1874;  and  Milwaukee,  Wis.,  in  1875. 

The  process  for  making  natural  cement  is  in  general  as  follows : 
The  rock  is  blasted  down  from  the  face  of  the  quarry,  broken  by 
hand  with  sledges  into  sizes  suitable  for  the  kiln,  loaded  on  dump 
cars  and  elevated  to  the  mouth  of  the  kilns.  Here  the  rock  is 
dumped  into  the  kiln  alternately  with  coal,  a  layer  of  rock  and 
then  a  layer  of  coal.  The  charging  is  kept  up  continuously  dur- 
ing the  daytime  but  hardly  ever  at  night.  As  the  charge  works 
its  way  down  through  the  kiln  it  becomes  calcined  and  the  larger 
portion  of  its  carbonic  acid  driven  off.  When  it  reaches  the  base 
of  the  kiln  it  is  drawn  out  and  conveyed  to  the  grinding  machin- 
ery. The  kilns  used  for  the  manufacture  of  natural  cement  are 
usually  made  of  iron  plates  riveted  together  and  lined  with  fire- 

1  Lesley— Jour.  Assoc.  Eng.  Socs.,  Vol.  XV.,  p.  198. 


MORTAR   MATERIALS  AND  CEMENT  INDUSTRY 


brick.  They  are  circular  in  shape,  upright,  and  their  average 
dimensions  are  about  16  feet  in  diameter  by  45  feet  in  height. 

The  clinker  is  usually  ground  by  buhr-stones,  the  fine  material 
in  many  mills  being  separated  from  the  coarse  by  passing  over 
screens,  so  placed  as  to  allow  the  fine  particles  to  go  to  the  store- 
house and  to  return  the  coarse  ones  to  the  grinders.  The  buhr- 
stones  are  preceded  by  crushers  or  crackers  to  reduce  the  clinker 
to  a  suitable  size  for  them  to  handle.  In  some  instances  ball  and 
tube  mills  and  Griffin  mills  have  been  installed  in  natural  cement 
plants,  particularly  where  these  plants  also  make  Portland,  but 
the  clinker  from  these  kilns  is  usually  so  soft  as  to  be  easily 
ground  by  buhr-stones. 

There  were  at  one  time  in  this  country  between  60  and  70  mills 
manufacturing  natural  cement,  now  there  are  very  few  in  opera- 
tion. Below  are  some  figures  on  the  production  of  natural  ce- 
ment in  this  country. 

TABLE  III.— PRODUCTION  OF  NATURAL  CEMENT"  IN  UNITED 

STATES,  1818-1908. 
(Mineral  Resources  of  the  United  States,  1909.) 


Year 

Barrels 

Year 

Barrels 

Year 

Barrels 

1818  to  1830  !     300,000 

1886 

4,186,152 

1898 

8,418,924 

1830101840      1,000,000 

1887 

6,692,744 

1899 

9,868,179 

1840  to  1850     4,250,000 

1888 

6,253,295 

J900 

8,383,519 

1850  to  1  860  j   11,000,000 

I889 

6,531,876 

1901 

7,084,823 

1860  to  1870 

16,420,000 

1890 

7,082,204 

1902 

8,044,305 

1870  to  1880 

22,OOO,OOO 

1891 

7,451,535 

I9°3 

7,030,271 

1880 

2,030,000 

1892 

8,211,  181 

1904 

4,866,331 

1881 

2,440,000 

1893 

7,4H,8i5 

1905 

4,473,049 

1882 

3,165,000 

1894 

7,563,488 

1906 

4,055,797 

1883 

4,190,000 

1895 

7,741,077 

1907 

2,887,700 

1884 

4,000,000 

1896 

7,970,450 

1908 

1,686,682 

1885 

4,100,000 

I897 

8,311,688 

1909 

1,527,279 

It  will  be  noticed  that  there  was  but  little  increase  in  the  pro- 
duction of  natural  cement  from  1887  to  1903  and  that  since  the 
latter  date  there  has  been  a  steady  decline.  This  is  due  to  the 
fact  that  since  about  1900  Portland  cement  has  been  fast  dis- 
placing natural  cement.  The  increase  in  production  in  1900 
was  due  to  the  strong  demand  for  building  materials  that  year; 


IO  PORTLAND  CEMENT 

a  demand  that  could  not  be  supplied  by  the  Portland  cement 
manufacturers.  Our  imports  in  1900  were  over  3,000,000  bar- 
rels of  Portland,  in  spite  of  the  fact  that  the  home  mills  pro- 
duced over  3,000,000  barrels  more  than  in  1899. 

Beginning  of  the  Portland  Cement  Industry  in  the  United  States. 

As  we  have  stated  cement-rock  was  discovered  in  1850  at  Sieg- 
fried, in  Northampton  Co.,  Pa.,  on  the  line  of  the  Lehigh  Coal 
and  Navigation  Co.'s  canal  leading  from  Easton  to  Mauch  Chunk. 
As  the  cement  for  the  canal  had  to  be  brought  from  New  York, 
the  discovery  was  a  valuable  one  and  was  put  to  immediate  use 
by  the  erection  of  a  mill  at  Siegfried. 

In  the  spring  of  1866,  Messrs.  David  O.  Saylor,  Esaias  Rehrig 
and  Adam  Woolever,  three  gentlemen,  of  Allentown,  Pa.,  formed 
the  Coplay  Cement  Co.,  and  located  a  mill  at  Coplay,  near  Allen- 
town,  and  not  far  from  Siegfried.  Mr.  Saylor  was  president 
and  superintendent  of  the  company.  The  plant  made  excellent 
cement  though  its  methods  for  doing  so  were  crude.  Early  in  the 
seventies  Mr.  Saylor  began  to  experiment  upon  the  manufacture 
of  Portland  cement  from  the  rocks  of  his  quarry.  No  Portland 
cement  was  made  in  this  country  then,  and  most  of  it  in  use  here 
came  from  England  and  Germany.  Its  reputation  was  established 
and  it  was  looked  upon  as  superior  to  Rosendale  cement. 

Mr.  Saylor  was  led  to  make  his  experiments  by  the  fact  that  he 
noticed  the  harder  burned  portions  of  his  Rosendale  clinker  gave 
a  cement  which  for  a  short  period  would  show  a  tensile  strength 
equal  to  that  of  the  best  imported  Portland;  but  he  found  this 
cement  would  crumble  away  with  time.  This  was  due  to  the  raw 
materials  not  being  properly  proportioned.  The  result  of  these 
experiments  taught  him  that  if  he  mixed  a  certain  amount  of 
cement-rock  high  in  lime  with  his  ordinary  cement-rock  he  could 
make  Portland  cement,  and  after  many  trial  lots  were  burned  the 
company  turned  out  its  first  Portland  in  1875.  This  was  the  first 
Portland  cement  made  in  the  Lehigh  District,  and  it  was  made 
from  a  material  totally  different  from  that  used  in  any  of  the 
European  mills. 


MORTAR  MATERIALS  AND  CEMENT  INDUSTRY  II 

The  drawings  for  the  first  kilns  were  made  by  James  Cabott 
Arch,  an  English  engineer,  and  were  bottle-shaped. 

Having  solved  the  problem  of  how  to  make  Portland  cement. 
Saylor  found  another  and  equally  difficult  one  awaiting  him  of 
how  to  sell  it,  after  it  was  made.  The  labor  cost  of  manufactur- 
ing his  cement  was  great  and  he  could  not  afford  to  offer  it  at 
prices  much  below  the  imported  article.  As  the  foreign  cements 
had  an  established  record,  they  fought  the  new  cement  with  the 
argument  that  any  brand  of  Portland  cement  required  time  to 
prove  itself,  and  it  was  only  by  liberal  advertising  and  an  iron- 
clad guarantee  of  his  product  that  Saylor  secured  a  market. 

Among  the  first  great  engineering  works  upon  whose  construc- 
tion Saylor's  Portland  cement  was  used  were  the  Eads  jetties 
along  the  Mississippi  River,  and  the  first  great  sky-scraper  in 
which  American  Portland  cement  was  used  was  the  Drexel  Build- 
ing in  Philadelphia.  Slowly  American  Portland  cement  overcame 
the  prejudice  against  it  and  it  is  now  recognized  as  superior  to 
that  manufactured  in  any  part  of  the  world.  Saylor's  original 
plant  turned  out  only  1,700  barrels  of  Portland  cement  a  year. 
Since  its  inception,  however,  it  has  grown  steadily  and  now  has  a 
capacity  of  considerably  over  this  amount  a  day. 

Development  in  Other  States. 

While  Saylor  was  conducting  his  experiments  in  the  Lehigh 
Valley,  a  Chicago  concern,  known  as  the  Eagle  Portland  Cement 
Co.,  built  a  plant  near  Kalamazoo,  Mich.,  about  1872,  to  manu- 
facture Portland  cement  from  marl  and  clay.  This  plant  at  first 
consisted  of  two  bottle-shaped  kilns,  which  number  was  after- 
wards increased  to  four.  The  product  was  known  as  "Eagle 
Portland  Cement,"  and  its  quality  must  have  been  excellent  as 
some  three  or  four  miles  of  sidewalk  put  down  in  Kalamazoo  are 
still  in  good  condition.  This  mill,  however  was  forced  to  shut 
down  in  1882,  for  although  its  product  sold  from  $4  to  $4.25 
per  barrel,  it  could  not  manufacture  cement  at  a  figure  below  this. 
Today  no  traces  of  even  the  kilns  remain.1 

At  Wampum,  Pa.,  a  small  plant  was  started  to  make  cement 

1  Russell— Twenty-second  Annual  Report,  U.  S.  Geological  Survey,  Part  III. 


12  PORTLAND   CEMENT 

from  limestone  and  clay,  in  1875.  Thomas  Millen  found,  at  South 
Bend,  Ind.,  a  white  marl  and  clay  which  resembled  in  composi- 
tion, the  material  used  for  cement  making  in  England,  and  started 
a  small  plant  there  in  iS//.1  Both  the  plants  at  Wampum  and 
South  Bend,  Ind.,  were  for  many  years  producers,  though  in  a 
modest  way.  In  Maine  also  a  small  plant  was  started  by  the 
Cobb  Lime  Co.,  at  Rockport,  in  1879,  but  this  too  failed  to  make 
cement  at  a  figure  below  its  selling  price  and  closed  down  perma- 
nently as  did  also  a  small  plant  in  the  Rosendale  district  about  the 
same  time. 

Of  the  six  works  started  prior  to  1881  half  that  number  were 
failures  and  represented  a  complete  less  to  their  promoters.  The 
cement  made  at  Coplay  and  Wampum,  however,  was  on  exhibi- 
tion at  the  Philadelphia  Centennial  in  1876  and  held  its  own  with 
the  imported  article. 

About  1883,  a  small  plant  for  the  manufacture  of  Port- 
land cement  was  inaugurated  at  Egypt,  Pa.,  near  Coplay,  by 
Robt.  W.  Lesley,  the  first  president  of  the  recently  formed 
American  Association  of  Portland  Cement  Manufacturers,  John 
W.  Eckert,  Saylor's  first  chemist,  and  others.  This  plant  pro- 
gressed gradually  and  developed  into  the  American  Cement 
Co.,  now  a  large  producer  of  both  natural  and  Portland  ce- 
ment. From  this  time  on  plants  sprung  up  rapidly  in  the  Lehigh 
Valley  Section,  among  the  older  ones  being  the  Atlas,  Bonneville, 
Alpha  and  Lawrence,  all  except  the  second  now  important  pro- 
ducers. 

In  other  sections  also,  successful  mills  were  built.  In  New 
York,  Thomas  Millen,  who  had  previously  built  a  works  in  In- 
diana, and  his  son,  Duane  Millen,  started  the  Empire  Portland 
Cement  Co.,  at  Warners,  Onondaga  Co.,  in  1886.  In  Ohio,  at 
Harper,  Logan  Co.,  the  Buckeye  Portland  Cement  Co.,  put  in 
operation  their  plant  in  1889;  and  in  1890  the  Western  Portland 
Cement  Co.,  of  Yankton,  S.  D.,  began  to  make  Portland  cement. 

From  this  time  on  the  Portland  cement  industry  has  taken  rapid 
strides  and  plants  have  been  built  in  almost  every  part  of  the. 

1  Cement  Age.  July,  1905,  contains  an  interesting  account  by  Mr.  Millen  himself  of 
how  he  came  to  go  into  the  manufacture  of  Portland  cement  at  South  Bend. 


MORTAR  MATERIALS  AND  CEMENT  INDUSTRY 


country.  The  process  of  manufacture  has  been  greatly  improved, 
resulting  in  a  considerable  lessening  of  the  cost  of  production. 
American  Portland  cement  has  practically  displaced  the  imported 
article.  New  uses  have  been  found  for  Portland  cement  and  it 
is  coming  rapidly  to  the  front  as  a  material  of  construction.  The 
new  American  Association  of  Portland  Cement  Manufacturers 
formed  in  1902,  promises  to  do  wonders  for  the  industry  and  to 
the  end  of  showing  the  many  uses  to  which  Portland  may  be  ap- 
plied with  advantage,  erected  a  building  and  prepared  to  exhibit 
for  the  Louisiana  Purchase  Exposition  at  St.  Louis  during  1904. 
This  association  has  also  published  and  distributed  gratis  to  those 
interested  valuable  bulletins  explaining  certain  particular  forms 
of  concrete  construction  and  the  employment  of  cement  by  the 
farmer  and  artesan. 

The  National  Association  of  Cement  Users  has  also  been  a 
potent  factor  in  popularizing  the  use  of  concrete.  This  societv 
holds  an  annual  meeting  at  which  papers  dealing  with  cemeu^ 
products  and  concrete  are  read.  In  addition  to  the  National 

TABLE  IV.— PRODUCTION  OF  PORTLAND  CEMENT  IN  THE  UNITED 
STATES,  1870-1909,  IN  BARRELS. 


Year 

Quantity 

Value 

Year 

Quantity 

Value 

1870-1879  . 
jggo  

82,OOO 
42,OOO 
6o,OOO 
85,000 
90,000 

IOO.OOO 
150,000 
150,000 
250,000 
250,000 

300,000 
335,500 
454.813 
547,440 
590.652 

$  -246,000 
I26,OOO 
150,000 
191,250 
193,500 

210,000 
292,500 
292,500 
487,500 
487,500 

500,000 
704,050 
967,429 
I,I53,600 
1,158,138 

1894  
1895  
1896  

1897  
1898  

1899  
1900  
1901  
1902  
1903  -  ... 

1904  
1905  
1906  

I907  
1908  

1909  

798,757 
990,324 
1,543,023 

2,677,775 
3,692,284 

5,652,266 
8,482,020 
12,711,225 
17,230,644 
22,342,973 

26,505,881 
35,246,812 
46,463,424 
48  785,390 
51,072,912 

62,508,461 

|  1,383,473 
1,585,830 
2,424,011 
4,315,891 
5.970,773 

8,074,371 
9,280,525 
12,532,360 
20,864,078 
27,713,319 

23,355,119 
33,245,867 
52,466,186 
53,992,551 
43,547,679 

50,510,385 

!88i  

!882  

1881  .  . 

1884 

T«8^ 

1886 

1887  

!888  

1889 

1890  • 

1891  . 

1892  
180-?  .  . 

395,567,395 



PORTLAND   CEMENT 


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1 

MORTAR  MATERIALS  AND  CEMENT  INDUSTRY 


TABLE  VI. — PRODUCTION  AND  CONSUMPTION  OF  PORTLAND  CEMENT 
IN  THE  UNITED  STATES. 


Per  capita  consumption  in  Ibs. 


200 


Production  in  barrels. 

60,000,000 


50,000000 


40,000,000 


30X500.000 


20,000,000 


10,000,000 


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1 6  PORTLAND  CEMENT 

Association  there  are  a  number  of  local  and  state  associations. 
Cement  shows  have  been  held  annually  at  Chicago  in  the  Col- 
osseum at  which  various  appliances  of  use  to  cement  workers 
were  on  exhibition  as  well  as  novel  cement  products,  etc. 

Tables  IV  and  V  show  the  growth  of  the  American  Port- 
land Cement  industry  and  Table  VI  gives  a  graphic  comparison 
of  the  production  and  per  capita  consumption  of  Portland  and 
Natural  cements  from  1890  to  1909. 


Chapter  II. 

THE  NATURE  AND  COMPOSITION  OF  PORTLAND  CEMENT. 

Portland  cement  may  be  defined  as  "the  finely  pulverized  pro- 
duct resulting  from  the  calcination  to  incipient  fusion  of  an  inti- 
mate mixture  of  properly  proportioned  argillaceous  and  calcar- 
eous materials  and  to  which  no  addition  greater  than  three  per 
cent,  has  been  made  subsequent  to  calcination.1" 

\Yhen  the  fine  powder  is  mixed  writh  water  chemical  action 
takes  place,  and  a  hard  mass  is  formed.  The  change  undergone 
by  the  cement  mortar  in  passing  from  the  plastic  to  the  solid  state 
is  termed  "setting."  This  usually  requires  but  a  few  hours  at 
most.  On  completion  of  the  set  a  gradual  increase  in  cohesive 
strength  is  experienced  by  the  mass  for  some  time,  and  the  cement 
is  said  to  "harden."  Cements  usually  require  from  six  months  to 
a  year  to  gain  their  full  strength.  Cement  differs  from  lime  in 
that  it  hardens  while  wet  and  does  not  depend  upon  the  carbon 
dioxide  of  the  air  for  its  hardening.  It  is  very  insoluble  in  water 
and  is  adapted  to  use  in  moist  places  or  under  water  where  lime 
mortar  would  be  useless. 

Composition  of  Poriland  Cement. 

The  composition  of  Portland  cement  may  be  considered  from 
two  viewpoints,  that  of  the  analyst  and  that  of  the  physical  chem- 
ist. To  ascertain  by  the  methods  of  the  former  the  ultimate2  oc 
elementary  composition  was  until  recently  considered  a  simple 
matter.  To  determine  by  synthesis  and  the  microscope  the  proxi- 
mate composition,  or  the  relation  which  these  elementary  com- 
pounds bear  to  each  other,  has  so  far  baffled  the  skill  of  some  of 
our  best  physical  chemists,  though  we  are  now  much  nearer  the 
solution  of  the  problem  than  formerly. 

1  Standard  Specifications,  Amer.  Soc.  Test.  Mat.,  etc. 

2  The  words  "ultimate  composition  "  are  here  used  in  contradistinction  to  "  proximate 
composition,"  the  former  meaning  merely  the  percentage  of  certain  elementarv  com- 
pounds that  are  shown  to  be  present  by  chemical  analj'sis,  and  the  latter  designating  the 
relation  which  these  bear  to  one  another. 


i8  PORTLAND 

The  present  state  of  the  art  of  cement  analysis  is  by  no  means 
as  satisfactory  as  it  might  be,  and  expert  and  careful  chemists 
do  not  always  agree  upon  even  the  ultimate  composition  of  ce- 
ment. After  the  careful  work1  done  by  two  committees  and  one 
of  the  best  chemists  of  the  United  States  Geological  Survey,  it 
would  seem  as  if  the  conditions  for  accurate  work  had  been  so 
fully  established  as  to  insure  agreement  among  skillful  chemists. 
That  this  is  not  so  the  following  incident  will  show.  Some  years 
ago  the  author  was  associated  with  two  prominent  American 
chemists  in  the  examination  of  some  30  samples  of  cement.  The 
average  results  of  the  three  sets  of  determinations  are  given  be- 
low and  demonstrate  clearly  how  unsatisfactory  is  the  present 
state  of  analytical  chemistry. 

Variation 

between 

~*-T-~^-*  ABC  extremes 

Ivime 60.75  61.13  61.19  0.46 

Silica 22-59  22.28  22.11  0.48 

Alumina  ;..-•  6.88  7.56  8.59  1.71 

Iron  oxide 3.40  3.61  2.56  0.84 

Magnesia 1.20  0.92  1.58  0.66 

Sulphur  trioxide 1.09  1.20  1.31  0.22 

Loss  on  ignition 2.22  2.22  2.37  0.25 

Considering  our  knowledge  of  the  proximate  composition  of 
cement,  the  situation  is  even  more  unsatisfactory. 

Le  Chatelier's  Investigations. 

Le  Chatelier2  in  1887  published  as  his  thesis  for  the  degree 
of  doctor  of  science  a  dissertation  upon  the  "Experimental  Study 
of  the  Constitution  of  Hydraulic  Mortars,"  in  which  he  pro- 
pounded the  theory  that  Portland  cement  was  composed  of  two 
essential  compounds,  tricalcium  silicate,  3CaO.SiO2,  and  trical- 
cium  aluminate  3CaO.Al,2OG.  He  arrived  at  this  conclusion 

1  Richardson,  Schaffer  and  Newberry— y.  Soc.  Chem.  Ind.,  21,  830  and  1216;  J.  Am. 
Chem.  Soc.,  25,  1180,  and  26,  995. 

Meade,  Newberry  and  McCready— Cement  and  Eng.  Neius,  Aug.,  1904,  Chem.  Eng.,  i. 
Hillebrand— y.  Am.  Chem.  Soc.,  24,  362. 

Peckham— y.  Soc.  Chem.  Ind.,  21,  831,  andy.  Am.  Chem.  Soc.,  26,  1636. 
Blount— y  Am.  Chem.  Soc.,  26,  995. 
Gano— Chem.  Eng.,  9,  7. 

1  Constitution  of  Hydraulic  Mortars,   (Trans,  by  Mack),  and  Annales  des  Mines,  1887,  N 
P-  345- 


NATURE  AND   COMPOSITION   OF   PORTLAND   CEMENT  19 

after  a  long  series  of  experiments,  which  consisted  in  examining 
thin  sections  of  cement  clinker  under  the  polarizing  microscope. 
He  also  made  experiments  upon  the  synthetic  production  of  cal- 
cium silicates  and  aluminates  by  heating  intimate  mixtures  of 
finely  pulverized  silica,  alumina,  and  lime.  He  then  examined 
into  the  hydraulic  properties  of  the  compounds  so  prepared.  He, 
however,  failed  to  prepare  the  tricalcium  silicate  directly  by 
heating  lime  and  silica,  the  result  of  the  attempt  being  a  mixture 
of  lower  silicates  and  lime,  but  gave  it  as  his  opinion  that  this 
compound  could  be  prepared  indirectly  by  heating  together  a 
mixture  of  fusible  silicates  and  lime. 

Assuming  that  three  molecules  of  lime  are  united  to  one  of  sil- 
ica to  form  the  tricalcium  silicate,  that  three  molecules  of  lime 
are  united  to  one  of  alumina  to  form  the  tricalcium  aluminate, 
and  that  these  two  compounds  are  the  essential  ingredients  of 
cement,  Le  Chatelier  gives  the  following  as  the  ratio  between  the 
lime  and  magnesia,  the  basic  elements,  and  the  silica  and  alumina, 
thexacid  elements  in  a  good  cement 

CaO  +  MgO< 
SiO,  +  Al,03=3 
and 

CaO  +  MgO        > 


Le  Chatelier  also  states  that  ( I )  usually  gives  for  a  good  cement 
from  2.5  to  2.7,  and  (2)   from  3.5  to  4. 

Ten  years  later,  Messrs.  Spencer  B.  and  W.  B.  Newberry1 
confirmed  the  views  of  Le  Chatelier  so  far  as  tricalcium  silicate 
was  concerned,  but  advanced  the  theory  that  the  alumina  was 
present  as  dicalcium  aluminate,  2CaOAl,O3.  They  prepared 
silicates  and  aluminates  of  lime  synthetically  just  as  did  Le 
Chatelier  by  heating  together  in  a  Fletcher  gas  furnace  intimate 
mixtures  of  finely  pulverized  quartz  and  calcium  carbonate,  and 
of  alumina  and  calcium  carbonate  in  different  molecular  pro- 
portions. They  then  examined  into  the  hardening  and  setting 
properties  of  the  resulting  compounds.  They  found  no  difficulty 

1 J.  Soc.  Chcm.  Ind..  n,  1035. 


2O  PORTLAND 

in  preparing  the  tricalcium  silicate  directly,  by  heating  together 
silica  and  lime  in  the  molecular  proportion  of  I  to  3.  The 
Messrs.  Newberry,  however,  from  their  experiments  upon  the 
calcium  aluminates  concluded  that  the  alumina  is  in  combination 
with  the  lime  as  dicalcium  aluminate  and  not  as  tricalcium  alumi- 
nate.  Their  experiments  led  them  to  the  following  conclusions : 

"First. — Lime  may  be  combined  with  silica  in  the  proportion 
of  3  molecules  to  i,  and  still  give  a  product  of  practically  constant 
volume  and  good  hardening  properties,  though  hardening  very 
slowly.  With  35^  molecules  of  lime  to  i  of  silica  the  product  is 
not  sound,  and  cracks  in  water. 

"Second. — Lime  may  be  combined  with  alumina  in  the  propor- 
tion of  2  molecules  to  i,  giving  a  product  which  sets  quickly,  but 
shows  constant  volume  and  good  hardening  properties.  With  2^ 
molecules  of  lime  to  I  of  alumina  the  product  is  not  sound." 

Newberry 's  Formula. 

The  formula  for  the  tricalcium  silicate,  3CaO.SiO2,  corre- 
sponds to  2.8  parts  by  weight  of  lime  to  i  part  of  silica,  and  the 
formula  for  the  dicalcium  aluminate,  2CaO.Al5O3,  corresponds 
ot  i.i  parts  of  lime  to  i  of  alumina.  From  this  the  following 
formula  is  given  as  representing  the  maximum  of  lime  which 
should  be  present  in  a  correctly  balanced  Portland  cement;  per 
cent,  lime  =  per  cent,  silica  X  2.8  +  per  cent,  alumina  X  i.i. 

They  found  that  cement  prepared  synthetically  with  lime, 
alumina,  and  silica  proportioned  according  to  the  above  formula 
gave  good  results,  whereas  that  prepared  by  Le  Chatelier's  for- 
mula was  unsound,  showing  the  lime  to  be  in  excess. 

Tornebohtn's  Investigations. 

Tornebohm,1  a  Swedish  investigator,  checked  the  microscopic 
work  of  Le  Chatelier  and  identified  in  Portland  cement  four  dis- 
tinct mineral  constituents  which  he  called  Alit,  Belit,  Felit  and 
Celit,  and  described  as  follows2 : — 

"Alit  is  the  preponderating  element  and  consists  of  colorless 
crystals  of  rather  strong  refractive  power,  but  of  weak  double  re- 

1  Kongreb  des  intern  verb,  fur  material  priiff  Stokholm,  1897. 
3  Richardson— Papers  Asso.  Port.  Cem.  Mfgs.,  June  15,  1904. 


NATURE   AND   COMPOSITION   OF   PORTLAND  CEMENT  21 

fraction.  By  this  he  means  that  Alit  in  polarized  light  between 
crossed  Nicol  prisms  has  insufficient  optical  activity  to  produce 
more  than  weak  interference  colors  of  a  bluish  gray  order. 

"Celit  is  recognized  by  its  deep  color,  brownish  orange.  It  fills 
the  interstices  between  the  other  constituents  and  eventually 
forms  the  magma  or  liquid  of  lowest  freezing  point  out  of  which 
the  Alit  is  separated.  It  is  strongly  double  refractive,  that  is  to 
say,  gives  brilliant  colors  when  examined  between  crossed  Nicol 
prisms. 

"Belit  is  recognized  by  its  dirty  green  and  somewhat  muddy 
color  and  by  its  brilliant  interference  colors.  It  is  bi-axial  and  of 
high  index  of  refraction.  It  forms  small  round  grains  of  no  rec- 
ognized crystalline  character. 

"Felit  is  colorless.  Its  index  of  refraction  is  nearly  the  same  as 
that  of  Belit  and  it  is  strongly  double  refractive.  It  occurs  in  the 
form  of  round  grains,  often  in  elongated  form,  but  without  crys- 
talline outline.  Felit  may  be  entirely  wanting. 

"Besides  these  minerals  an  amorphous  isotropic  mass  was  de- 
tected by  Tornebohm  and  Le  Chatelier.  It  is  called  isotropic  be- 
cause it  has  no  effect  upon  polarized  light.  It  has  a  very  high  re- 
fractive index. 

"Tornebohm  adds  the  important  fact  that  a  cement  4  per  cent, 
richer  in  lime  than  usual  consists  almost  entirely  of  Alit  and 
Celit." 

Richardson's  Work. 

Clifford  Richardson,  an  American  chemist,  in  two  papers,  read 
before  the  Association  of  American  Portland  Cement  Manufac- 
turers, June  15  and  December  14,  1904,  described  the  results  of  a 
thorough  and  exhaustive  microscopic  study  of  Portland  cement 
clinker.  As  the  result  of  this  investigation  he  again  advanced 
the  theory  first  brought  forward  by  Winkler1  in  1858,  I  believe, 
that  Portland  cement  clinker  is  a  solid  solution.  This  paper  was 
one  of  the  first  attempts  to  explain  the  properties  of  cement  along 
the  lines  of  physical  chemistry,  and  the  investigations  which  led 
up  to  it  were  very  thorough.  Richardson  prepared  many  syn- 

1  Dingier' 3  polyt.  Jour..  175,  p.  208. 


22  PORTLAND 

thetic  silicates  and  aluminates  and  determined  their  optical  prop- 
erties, hydraulic  value  and  physical  characteristics. 

Richardson  next  prepared  clinkers  of  pure  silica.  Alumina, 
and  lime  in  the  proportions  met  with  in  the  industrial  product 
and  thin  sections  of  these  clinkers  were  then  examined  under 
the  microscope.  As  the  result  of  this  investigation,  he  gave  as 
his  opinion  that  the  Alit  of  Tornebohm,  the  essential  constituent 
of  Portland  cement,  was  a  solid  solution  of  tricalcium  silicate, 
SiCyCaO,  in  tricalcium  aluminate,  Al2O33CaO,  and  that  Celit 
was  a  solid  solution  of  one  dicalcium  compound  in  the  other. 

Richardson  also  concluded  that  the  setting  of  Portland  cement 
is  almost  entirely  due  to  the  decomposition  of  the  Alit,  examina- 
tion showing  the  Celit  to  be  almost  unattacked;  and  that  the 
strength  of  Portland  cement  after  setting  is  due  entirely  to  the 
crystallization  of  calcium  hydrate  under  certain  favorable  condi- 
tions, and  not  at  all  to  the  hydration  of  the  silicates  and  alumi- 
nates. His  theory  was  that  "on  addition  of  water  to  the  stable 
system  made  up  of  the  solid  solutions  which  compose  Portland 
cement,  a  new  component  is  introduced,  which  immediately  results 
in  lack  of  equilibrium,  which  is  only  brought  about  again  by  the 
liberation  of  free  lime.  This  free  lime  the  moment  that  it  is  lib- 
erated, is  in  solution  in  the  water,  but  owing  to  the  rapidity  with 
which  it  is  liberated  from  the  aluminate,  the  water  soon  becomes 
supersaturated  with  calcic  hydrate  and  the  latter  crystallizes  out 
in  a  network  of  crystals,  which  binds  the  particles  of  undecom- 
posed  Portland  cement  together."  The  initial  set  is  due  to  the 
aluminates,  while  subsequent  hardening  is  due  to  the  slower  lib- 
eration of  lime  from  the  silicates. 

Researches  of  Day  and  Shepherd.1 

In  June,  1906,  Day  and  Shepherd,2  in  a  paper  read  at  the  Ithaca 
meeting  of  the  American  Chemical  Society,  stated  that  no  such 
compound  as  tricalcium  silicate  exists  and  that  the  compound  so- 
called  by  others  is  merely  a  mixture  of  lime  and  calcium  ortho- 
silicate  (dicalcium  silicate).  The  reasoning  and  work  upon 

1  The  author  is  indebted  to  Dr.  E.  S.  Shepherd  for  the  following  summary  of  his  most 
recent  investigations  at  the  Carnegie  Institution  upon  the  composition  of  cement. 

2  Am.  Chent.  Soc.t  a8,  1089,  also  abstract  from  Chem.  Eng.,  4,  273. 


NATURE  AND   COMPOSITION   OF   PORTLAND   CEMENT  23 

which  these  latter  investigators  based  their  conclusions  appeared 
to  be  so  satisfactory  as  to  completely  overthrow  the  theories  of 
their  predecessors — Richardson  himself  acknowledging  the  prob- 
ability that  they  are  right.1 

At  that  time,  Day  and  Shepherd  were  led  to  the  conclusion 
that  tricalcic  silicate  did  not  exist  by  the  following  reasons: 

1.  Preparations   of  this   composition   when   fused   and   exam- 
ined by  very  refined  optical  methods  were  found  to  consist  of 
crystallized  lime  and  orthosilicate   (dicalcic  silicate). 

2.  All  preparations  submitted  by  others  showed  the  same  con- 
stituents. 

3.  Certain  thermal  changes  characteristic  of  the  orthosilicate 
were   found  throughout  the   region   where  the  tricalcic   silicate 
should  have  occurred. 

4.  No  definite  proof  of  the  individuality  of  the  tricalcic  sili- 
cate composition  has  anywhere  appeared,  except  that  the  prep- 
arations made  of  this  composition  were  "volume  constant." 

These  facts  remain  unshaken,  but  more  recent  experiments 
have  explained  them  in  a  somewhat  different  manner. 

In  the  latest  paper  from  the  Geophysical  Laboratory  (Pre- 
liminary Report  on  the  Ternary  System  CaO — A12O3 — SiO2,  E. 
S.  Shepherd  and  G.  A.  Rankin,  with  an  optical  study  by  F.  E. 
Wright,  J.  I.  C.),  it  has  been  found  that  tricalcic  silicate  really 
exists,  but  that  it  has  rather  unusual  properties.  It  belongs 
to  that  class  of  compounds  which  form  by  reaction  between  the 
solid  particles  and  is  completely  destroyed  by  melting,  i.e.,  in  the 
simple  mixtures  of  lime  and  silica,  in  the  presence  of  alumina 
the  re-combination  is  more  rapid.  It  has  been  found  that  burn- 
ing the  appropriate  mixture  at  temperatures  below  1,900°  C., 
the  combination  of  the  lime  with  the  dicalcic  silicate  is  almost 
complete.  Very  small,  weakly  birefracting  crystals  result,  but 
their  optical  character  could  not  be  determined.  With  the  ad- 
dition of  0.5  per  cent,  of  alumina,  these  crystals  could  be  grown 
to  sufficient  size  for  good  determinations.  They  prove  to  be 
optically  negative  and  wholly  different  from  the  orthosilicate. 

1  Papers,  American  Cement  Manufacturers'  Association,  Sept.  12,  1906. 


PORTLAND 


A  somewhat  earlier  paper1  on  the  lime  aluminates,  developed  the 
following  definite  compounds :  3CaO.AL2O3,  5CaO.3Al2O3, 
CaO.Al2O3  and  3CaO.5Al2O3,  the  first  three  of  which  may  occur 
in  cement. 

The  complete  solution  of  the   ternary  diagram  allows   us   to 


ioo%c»o 


70  3CAO-ALA60 

Fig.  i.— Ternary  diagram. 


50  5C*0-3ALaO, 


divide  pure  cement  clinker  into  five  types.     A  portion  of  this 
diagram  is  given  in  Fig.  i 

In  this  figure  the  fields  enclosed  within  the  lines  joining: 


1  Binary  Systems  of  Alumina  with  Silica,  I^ime  and  Magnesia,  Am.  Jour.  Sci.,  28,  293, 


1909. 


NATURE   AXD    COMPOSITION    OF    PORTLAND   CEMENT  25 

1.  CaO-C-i8-i7-D  is  the  field  where  pure  CaO  is  the  primary 
phase,  i.e.j  the  first  to  separate  from  the  melt. 

2.  Between  18-16-17,  3CaO.SiO,  is  the  primary  phase. 

3.  C-B-6-i3-i4-i5-i6-i8  encloses  the  field  for  2CaO.SiO2. 

4.  D-i7-i6-E  encloses  the  field  for  3CaO.Al2O3. 

5.  E-I5-I4-F  is  the  field  for  5CaO.3Al263. 

6.  To  the  right  of  F-I4-I3,  CaO.Al2O3  is  the  primary  phase. 

7.  To  the  right  of  13-6,  2CaO.Al2O3.SiO2  is  the  primary  phase. 

8.  Above  6-B  is  the  field  for  CaO.SiO37  calcium  metasilicate. 
Type  I. — Clinker  containing  more  lime  than  corresponds  to  a 

mixture  of  3CaO.SiOe  and  3CaO.Al2O3  will  contain  free  lime 
and  will  freeze  solid  at  point  17  in  the  diagram  to  a  mixture 
of  CaO,  3CaO.SiO2  and  3CaO.Al2O3.1 

Type  II. — Clinkers  whose  composition  lies  within  the  triangle 
formed  by  joining  the  compositions  3CaO.SiO2,  3CaO.Al2O3  and 
2CaO.SiO2  will  freeze  solid  at  point  16  to  a  mixture  of 
3CaO.SiO2,  2CaO.SiO2  and  3CaO.Al2O3.  This  is  presumably 
the'  normal  type  of  cement  clinker. 

Type  III. — Clinker  whose  composition  lies  within  the  tri- 
angle formed  by  joining  the  compositions  2CaO.SiO2,  3CaO.Al2O3 
and  5CaO.3Al2O3  will  freeze  solid  at  point  15  to  a  mixture  of 
2CaO.SiO2,  3CaO.Al2O,  and  5CaO.3Al2O3.  This  would  perhaps 
correspond  to  the  type  of  low-limed  cements,  containing  less 
lime  than  called  for  by  the  formula  2CaO.SiO2  +  5CaO.3Al2O3. 

Type  IV. — Would  freeze  solid  at  point  14  to  a  mixture  of 
2CaO.SiO2,  5CaO.3Al2O3  and  CaO.Al2O3. 

Type  V . — Containing  still  less  lime,  would  be  a  very  low 
limed  Portland  or  a  very  high  limed  slag  clinker.  Presumably 
it  would  freeze  solid  at  point  13  to  a  mixture  of  2CaO.SiO2, 
2CaO.Al2O3.SiO2  and  CaO.Al2O3.  For  theoretical  reasons  the 
exact  nature  of  this  last  type  must  be  regarded  as  tentative. 
It  will  be  of  little  interest  to  Portland  Cement  makers. 

Instead  of  having  to  deal  with  a  mixture  of  only  two  com- 
pounds as  the  earlier  investigators  assumed,  it  appears  that 

1  In  this  discussion  we  must  assume  that  equilibrium  is  alwaj-s  attained  and  that  we 
are  dealing  with  mixtures  of  pure  CaO,  Al2O3  and  SiO2.  The  relations  in  a  commercial 
clinker  will  be  modified  by  the  impurities  present  and  the  effect  of  these  impurities 
(MgO.  FeoO3,  etc.)  remains  to  be  investigated. 


26  PORTLAND  CEMENT 

clinker  will  contain  at  least  three  different  compounds  whose 
reaction  with  water  may  now  be  studied  with  more  certainty. 
Some  one  of  these  five  types  ought  to  give  the  best  Portland 
cement,  so  that  with  the  knowledge  of  the  proper  mixtures  to 
be  studied  and  with  the  assistance  of  the  microscope  to  check 
the  preparation,  a  definite  standard  ought  to  be  readily  located. 
It  also  seems  that  the  microscope  properly  used  ought  to  give  a 
quick  and  reliable  test  as  to  the  quality  of  the  clinker. 

Uncertainty  as  to   the   Composition. 

Thus  we  find  in  the  last  twenty  years  three  radically  different 
theories,  each  generally  accepted  and  held,  for  a  time  at  least,  as 
to  the  proximate  composition  of  Portland  cement,  and  we  would 
expect  these  revolutions  of  theory  to  have  some  influence  upon  the 
practical  manufacture  of  Portland  cement  and  the  ultimate  com- 
position of  the  commercial  product.  This  is  not  the  case,  how- 
ever, and  the  effect  of  theory  of  composition  upon  practical 
cement  making  has  been  small.  In  1896  the  author  analyzed  a 
sample  of  Saylor's  cement  and  again  in  19x36  another.  It  is 
doubtful  if  both  samples  had  been  drawn,  at  either  time,  from 
cement  made  a  few  days  apart  if  they  would  have  agreed  more 
closely.  The  analyses  follow : 

1896  1906 

Silica    , 22.60  22.38 

Iron  oxide 2.30  2.50 

Alumina 6.70  6.80 

Lime 62.50  62.40 

Magnesia 3.38  3.12 

Sulphur  trioxide i .88  1.44 

It  must  not  be  supposed  from  the  foregoing,  however,  that 
American  cements  are  not  better  to-day  than  they  were  ten  years 
ago,  for  in  fact  they  are  on  an  average  much  better,  but  this 
progress  has  been  due  to  the  improved  mechanical  appliances 
rather  than  to  any  new  ideas  of  how  to  make  Portland  cement, 
brought  about  by  changes  of  our  theory  as  to  what  the  product 
really  is.  Nearly  all  investigators  who  attempted  to  prepare 
cement  of  varying  composition  called  attention  to  the  importance 


NATURE   AND   COMPOSITION   OF   PORTLAND   CEMENT  2/ 

of  fine  grinding  of  the  raw  materials,  but  most  mill  chemists  who 
were  at  all  observant  had  previously  noticed  the  relation  between 
the  fineness  of  the  raw  materials  and  "constancy  of  volume"  of 
the  resulting  product.  Great  improvements  have  been  made  in 
recent  years  in  grinding  machinery.  It  is  now  possible  to  not 
only  grind  the  raw  materials  much  finer  than  formerly,  but 
also  to  do  this  much  more  economically.  The  introduction 
of  mills  of  the  centrifugal  type,  such  as  the  Fuller-Lehigh 
Mill,  as  well  as  improvements  in  the  tube  mill  and  methods  of 
transmitting  power  to  the  mills  have  aided  materially  in  cheapen- 
ing the  grinding  of  the  raw  materials  to  the  point  where  the  in- 
troduction of  these  latter  into  the  kiln  at  a  fineness  of  from  95  to 
98  per  cent,  passing  the  No.  100  sieve  is  commercially  practicable. 

The  rotary  kiln  also  enabled  the  American  manufacturer  to 
improve  considerably  his  product,  as  this  kiln  burns  very  uni- 
formly when  properly  handled  and  no  sorting  of  the  clinker  is 
necessary. 

While  it  is  true  that  theory  has  not  helped  practice  in  the  past, 
the  author  believes  that  a  solution  of  the  question  of  the  proxi- 
mate composition  of  cements  would  be  of  practical  importance 
and  benefit.  Perhaps  the  reason  that  the  old  theories  have  not 
harmonized  with,  and  made  some  impression  upon,  the  practice 
of  Portland  cement  manufacture  is  because  of  the  fact  that  they 
were  wrong.  The  true  solution  of  the  problem  might  open  up 
many  avenues  of  investigation  which  would  lead  to  practical 
benefit  and  improvement  of  both  the  product  and  process  of  manu- 
facture. 

In  spite  of  the  uncertainty  as  to  the  proximate  composition  of 
Portland  cement,  the  general  influence  of  chemical  composition 
upon  physical  properties  is  well  understood  among  cement  tech- 
nologists ;  but  this  knowledge  must  be  credited  to  practical  ex- 
perience rather  than  scientific  theorizing.  The  controlling  of 
the  composition  of  the  cement  is  nearly  all  of  it  done  by  rule  of 
'thumb  methods,  and  each  chemist  employs  the  formula  which 
practical  experience  has  taught  him  best  suits  his  conditions.  The 
difference  in  raw  materials  and  manufacturing  conditions  no 


28  PORTLAND  CEMENT 

doubt  makes  this  necessary  and  no  formula  applicable  to  all  cases 
has  as  yet  been  proposed. 

Substances  found  in  Cement. 

Whatever  may  be  the  nature  of  their  combination  with  each 
other  the  essential  elements  of  Portland  cement  are  lime,  silica, 
and  alumina.  In  the  cements  of  commerce,  iron  replaces  some 
alumina  and  magnesia  some  lime,  since  clays  usually  contain  a 
considerable  amount  of  the  former,  and  limestones  are  rarely  free 
from  at  least  a  few-tenths  of  a  per  cent,  of  the  latter.  Other 
elements  which  are  found  in  one  or  the  other  or  even  both  of  the 
raw  materials  and  which  find  their  way  into  the  final  product  are 
the  alkalies,  manganese,  titanic  acid,  phosphoric  acid,  sulphuric 
acid  and  strontium.  Sulphate  of  lime,  either  in  the  form  of  gyp- 
sum, CaSO4.2HeO,  or  of  plaster  of  Paris  (CaSO4)2.H2O,  is 
added  to  regulate  the  setting  time,  and  carbon  dioxide  and  water 
are  absorbed  from  the  air  by  the  clinker,  either  before  or  after 
grinding.  Of  these  elements,  lime,  silica,  alumina,  iron  and 
sulphuric  acid  all  exercise  an  important  influence  on  the  cement, 
and  its  properties  will  depend  largely  upon  the  relative  amounts 
of  these  present.  .The  alkalies,  no  doubt,  if  present  in  larger 
quantities,  would  affect  to  some  degree  at  least  the  physical 
properties  of  cement,  but  in  the  small  amounts  found  in  American 
Portland  cements  the  role  they  play  is  a  very  slight  one.  Table 
VII  gives  the  analyses  of  a  larger  number  of  American  Portland 
cements  from  different  parts  of  the  country,  and  made  from 
various  raw  materials. 

Referring  to  Table  VII,  we  see  that  the  chemical  composition 
of  American  Portland  cements  which  pass  the  standard  speci- 
fications for  soundness,  setting  time  and  tensile  strength  falls 
within  the  following  limits: 

Per  cent. 

Silica 19—25 

Alumina  5—  9 

Iron  oxide 2 —  4 

Lime 60 — 64 

Magnesia i —  4 

Sulphur  trioxide i—  1.75 


NATURE   AND   COMPOSITION   OF   PORTLAND   CEMENT 


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3O  PORTLAND 

The  average  is  represented  by  the  fallowing: 

Per  cent. 

Silica 22.0 

Alumina 7-5 

Iron  oxide 2.5 

lyime 62.0 

Magnesia 2.5 

Sulphur  trioxide 1.5 

The  Lehigh  Valley  cements  (made  from  argillaceous  lime- 
stone) are  characterized  by  high  magnesia  usually  between 
3  and  3.5  per  cent.,  though  occasionally  as  low  as  2.5  per 
cent,  and  as  high  as  4  per  cent.  They  contain  about  2.5  per  cent, 
iron  oxide  and  about  twice  as  much  silica  as  iron  oxide  and 
alumina  combined.  In  those  cements  from  the  western  end  of 
the  deposit,  this  ratio  is  somewhat  higher,  however,  owing  to  the 
fact  that  the  cement-rock  found  here  is  higher  in  silica  and  also 
to  the  fact  that  the  limestone  used  with  this  rock  is  silicious. 

Most  of  the  marl  cements  are  low  in  magnesia,  some  of  them 
containing  as  little  as  0.5  per  cent.  Some  of  the  Michigan  marl 
cements  are  high  in  iron  oxide,  3  to  4  per  cent.  This  comes  from 
the  clay,  or  shale,  however,  and  hence  is  also  characteristic  of 
some  cements  made  from  limestone  and  clay  or  shale. 

The  Alabama  cements  made  from  the  Selma  chalk  at  Demopolis 
are  high  in  iron  and  alumina,  published  analyses  showing  12  to  14 
per  cent,  iron  oxide  and  alumina  and  only  about  20  per  cent  silica. 

Lime 

Most  American  cements,  which  meet  standard  specifications, 
contain,  when  freshly  made,  from  60  to  63.5  per  cent.  lime.  Since 
cements  absorb  water  and  carbon  dioxide  on  exposure  to  air, 
the  percentage  of  lime  and  also  of  all  other  elements,  except  the 
two  absorbed,  is  lowered  by  the  seasoning  or  storage  of  the 
cement.  In  comparing  the  analyses  of  two  cements,  therefore, 
the  amount  of  loss  on  ignition  should  always  be  considered,  as  a 
cement  containing  63  per  cent,  lime  when  fresh  may  contain  62 
per  cent,  or  even  less  after  exposure  to  air  for  a  month. 

Instead  of  comparing  two  cements  by  means  of  their  analyses  the 
better  way  is  to  determine  their  respective  "hydraulic  indices' 


J 


NATURE  AND   COMPOSITION   OF   PORTLAND   CEMENT  31 

or  the  reverse  of  this,  which  the  author  terms  "lime  ratio." 
The  hydraulic  index  is  generally  understood  to  mean  the  ratio 
between  the  silica  and  alumina  on  the  one  hand  and  the  lime  on 
the  other  or  expressed  mathematically: — 

-,    ,       ,.    .    ,  %  silica  -f  %  alumina 

Hydraulic  index  =  -  —  . 

%  lime 

The  authors  lime  ratio  is  the  reverse  of  this  and  takes  into 
consideration  the  iron  oxide  also. 

,  .  %  lime 

Lime  ratio  =  - — — —  — -j—. . 

%  silica  -f-  %  alumina  -}-  %  iron 

The  amount  of  lime  a  cement  may  contain  is  dependent  upon 
both  factory  conditions  and  the  relative  amount  of  silica  to  iron 
and  alumina  present.  The  maximum  of  lime  is  usually  con- 
trolled by  the  "soundness  tests"  (which  are  now,  in  America,  the 
boiling  and  steaming  of  small  pats  of  neat  cement  for  five  hours), 
i  The  minimum  of  lime  is  determined  by  the  setting  time  of  the 
cement,  which  must  be  such  that  the  cement  does  not  get  its 
initial  set  in  less  than  30  minutes,  and  also  the  strength  which 
should  be  at  least  450  Ibs.  neat  and  150  Ibs.  sand  per  sq.  inch. 
Over-limed  cements  are  "unsound,"  that  is,  in  time  concrete 
made  from  them  will  disintegrate  and  crumble  or  crack.  Ce- 
ments which  are  high  in  lime  without  being  unsound  are  slow 
setting  but  harden  rapidly,  sometimes  reaching  their  maximum 
strength  in  as  short  a  period  as  seven  days.  Such  cements,  when 
subjected  to  tension  tests,  usually  show  retrogression  as  the 
test  pieces  grow  older,  but,  when  subjected  to  compression  tests, 
show  an  increase  of  strength  with  age.  This  is  due  to  the  fact 
that  high  lime  cements  become  very  brittle  on  hardening,  hence 
when  they  are  tested  in  the  ordinary  manner  more  or  less  dis- 
tortion is  met  with,  owing  to  the  shortness  of  the  test  piece, 
and  the  briquette  is  snapped  off,  as  it  were,  and  not  really  pulled 
apart.  Provided  a  cement  is  sound  there  is  nothing  in  the 
theory  so  tenaciously  held  to  by  the  school  of  engineers  and 
chemists  who  borrow  their  ideas  from  the  text-books  of  the  past 
generation,  that  a  cement  must  show  a  progressive  gain.  A 
cement  which  gets  its  strength  promptly  is  certainly  much  better 


32  PORTLAND  CEMENT 

adapted  to  modern  building  conditions  than  one  which  requires 
a  long  period  to  reach  the  same  point.  With  such  a  cement, 
forms  can  be  promptly  removed  and  it  is  also  suited  to  work 
in  cold  weather,  such  as  in  thin  partitions  and  floors,  where 
slower  hardening  cement  would  be  impracticable,  owing  to  the 
length  of  time  during  which  it  is  necessary  to  protect  the  work 
from  the  weather. 

Cements  low  in  lime  usually  contain  clay  in  excess,  for  suffi- 
cient lime  was  not  originally  present  in  the  raw  material  to 
change  all  the  clay  to  silicates  and  aluminates.  This  excess  of 
clay,  of  course,  is  devoid  of  cementing  qualities  and  may  be 
looked  upon  as  just  so  much  foreign  matter.  Though  it  will 
not  cause  the  cement  to  fall  to  pieces  subsequently,  it  takes  away 
from  its  strength  because  in  its  place  should  be  cement.  Low 
lime  cements  are  apt  to  be  "quick-setting."  Hence,  one  of  the 
remedies  for  "quick-setting"  cement  is  to  increase  the  lime  con- 
tent of  the  raw  mixture.  For  this  reason  high  alumina  cements 
often  contain  more  lime  than  those  low  in  alumina,  in  spite  of 
the  fact  that  alumina  combines  with  less  lime  than  does  silica. 

The  amount  of  lime  a  cement  will  safely  carry  is  dependent  on 
the  relative  amounts  of  silica  and  alumina  present  and  also  on 
the  care  with  which  a  cement  is  made.  Practically  all  American 
cements  fall  between  two  limits,  i.  e,,  the  ratio  of  thdjpme  to 
the  silica,  iron  and  alumina  together  should  not  exceed  2.1:1 
nor  be  less  than  1.9:1.  To  make  a  sound  cement  having  the  first 
ratio  the  raw  materials  must  be  well  mixed  and  very  finely 
ground.  Such  a  cement  will  be  much  stronger,  however,  than 
one  having  the  lower  ratio. 

Anything  which  will  promote  the  combination  or  solution  of 
the  lime  during  burning  will  promote  soundness.  Thus  the  finer 
the  raw  materials  are  ground  the  more  surface  of  contact  be- 
tween the  acid  and  basic  elements  exists,  hence  fine  grinding  of 
the  raw  materials  is  probably  the  most  important  requisite  for 
the  making  of  a  sound  cement.  It  is,  of  course,  essential  that 
the  burning  should  be  carried  out  at  the  proper  temperature  and 
be  of  sufficient  duration  to  promote  combination  and  solution. 


NATURE  AND   COMPOSITION   OF   PORTLAND   CEMENT  33 

The  greatest  advance  in  the  manufacture  of  Portland  cement 
from  the  standpoint  of  quality  has  been  in  the  introduction  of 
more  efficient  grinding  machinery,  allowing  the  finer  grinding  of 
the  raw  materials  and  hence  the  manufacture  of  high  limed,  sound 
cements  of  great  strength. 

The  percentage  of  lime  to  be  carried  at  any  works  is  usually 
controlled  by  two  things,  the  "setting  time"  and  the  "soundness." 
There  must  be  enough  lime  present  to  keep  the  cement  from  be- 
ing quick-setting,  either  when  made  or  after  seasoning,  and 
there  must  not  be  so  much  lime  present  that  the  cement  will  not 
pass  the  soundness  tests. 

Silica  and  Alumina. 

Silica  and  alumina,  the  other  essential  constituents  in  Portland 
cement,  have  also  an  equally  important  bearing  on  the  strength. 
From  the  nature  of  things,  cements  high  in  alumina  are 
low  in  silica  and  those  low  in  alumina  are  high  in  silica. 
Cements  usually  contain  19  to  25  per  cent  silica  and  from  5  to 
9  per  cent,  alumina.  High  silica  cements  are  usually  slow-set- 
ting and  of  good  tensile  strength.  They  harden  also  slowly 
and  usually  show  a  progressive  gain.  High  alumina  cements 
are  apt  to  be  quick-setting  and  indeed  if  much  more  than  10  per 
cent,  alumina  is  present  the  cement  is  almost  sure  to  be  quick- 
setting  even  with  the  addition  of  sulphates.  High  alumina  ce- 
ments also  are  quick  hardeners  and  consequently  cements  con- 
taining from  7^  to  10  per  cent,  alumina  show  high  7-day  tests. 
Cements  should  contain  at  least  2.5  times  as  much  silica  as 
alumina.  This  ratio  between  the  silica  and  the  alumina  the 
author  calls  the  index  of  activity,  or 

T  j        s      j-  -j  % 

Index  of  activity  =  —  — 


. 
%  alumina 

This  index  should  lie  between  2.5  and  5.  Cements  with  an 
index  of  activity  of  less  than  2.5  are  apt  to  be  quick-setting  or 
else  to  become  quick-setting  on  exposure  to  air.  In  order  to  off- 
set this  tendency  to  set  quickly  on  the  part  of  high  alumina  ce- 
ments, it  is  necessary  to  make  them  relatively  higher  limed  than 
3 


34  PORTLAND  CEMENT 

those  containing  moderate  percentages  of  alumina.  The  high 
lime  content  gives  slow-setting  properties  which  offset  the  quick- 
setting  ones  due  to  high  alumina.  This  is  necessary  in  spite  of 
the  fact  that  silica  combines  with  more  lime  than  does  alumina. 
If  we  assume  both  the  silica  and  the  alumina  to  be  present  as 
tricalciumsilicates  and  tricalciumaluminates,  then  silica  combines 
with  1.7  times  as  much  lime  as  alumina.  On  the  other  hand 
alumina  increases  the  fluidity  of  the  magma,  and  hence  makes 
the  cement  more  easily  burned.  Indeed  cements  high  in  alumina 
are  hard  to  burn  properly,  owing  to  the  fusibility  of  the  calcium 
aluminate.  This  causes  balling  up  and  sticking  together  of  the 
clinker  in  the  hot  zone  of  the  kiln  preventing  uniform  burning. 
Cements  with  an  index  of  activity  of  more  than  5  are  usually 
very  hard  to  burn.  They  are  slow-setting  and  also  slow  hard- 
eners. Their  early  strength  is  often  low  but  ultimately  they  ob- 
tain as  great  strength  as  other  cements.  There  are  a  number 
of  high  silica  cements  on  the  American  market  which  have  great 
difficulty  in  meeting  standard  specifications  as  to  7-day  strength. 

Ferric  Oxide. 

According  to  Le  Chatelier,  ferric  oxide  and  calcium  carbonate 
on  burning  yield  products  which  slake  with  water  and  possess  no 
hydraulic  properties.  Schott,  however,  prepared  cement  contain- 
ing only  lime,  silica  and  ferric  oxide,  which  showed  excellent 
hardening  qualities,  and  therefore  concluded  that  alumina  could 
be  completely  replaced  by  ferric  oxide  without  diminishing  in  any 
way  the  hydraulic  properties  of  cement.  S.  B.  and  Wf  B.  New- 
berry  from  their  researches  concluded  that  ferric  oxide  and  alum- 
ina act  in  a  similar  manner  in  promoting  the  combination  of  silica 
and  lime.  Zulkowsky  also  made  experiments  along  this  line  and 
his  conclusions  agree  with  those  of  Schott  and  Newberry,  and 
it  is  now  generally  agreed  that  the  iron  oxide  in  the  cement 
mixture  acts  as  a  flux  and  promotes  the  combination  of  the 
silica  and  the  lime. 

Mixtures  of  silica,  alumina,  and  lime,  in  the  proportions 
usually  found  in  cement,  are  extremely  hard  to  burn.  The  re- 
placement of  part  of  the  alumina  by  iron,  however,  greatly  low- 


NATURE  AND   COMPOSITION   OF  PORTLAND   CEMENT  35 

ers  the  temperature  of  burning.  One  of  the  cures  for  unsound 
cement  is  therefore  found  in  the  replacement  of  clays  high  in 
alumina  by  those  high  in  iron.  As  iron  does  not  seem  to  make 
cement  quick-setting,  iron  may  be  made  to  replace  alumina  to 
advantage  in  many  instances.  In  mixtures  high  in  silica  and 
consequently  hard  to  burn,  the  addition  of  some  soft  iron  ore, 
such  as  brown  hematite,  to  the  mix  would  lower  the  tempera- 
ture at  which  clinkering  takes  place  and  make  it  easier  to  pro- 
duce a  sound  cement. 

Iron  on  the  other  hand  makes  a  very  hard  clinker  and  high 
iron  cements  have  been  found  very  hard  to  pulverize,  hence  in 
most  cases  it  will  be  found  more  economical  to  grind  the  raw 
materials  finer  than  to  add  iron  ore  and  produce  harder  grind- 
ing clinker.  High  silica  clinkers  are  relatively  speaking  soft. 

The  color  of  cement  is  also  due  to  iron.  Cement  made  from 
materials  containing  no  iron  is  perfectly  white.  It  requires  a 
higher  temperature  to  burn,  but  when  properly  clinkered  pos- 
sesses all  the  setting  and  hardening  properties  of  Portland  ce- 
ment. White  Portland  cements  are  now  made  at  a  number  of 
places  in  this  country.  The  author  recently  examined  some  of 
this  cement  and  his  results  follow : 

Analysis. 

Per  cent. 

Silica 23.56 

Iron  oxide 0.32 

Alumina   5-66 

Lime * 64.12 

Magnesia 1.54 

Sulphur  trioxide 1.50 

Loss  on  ignition 2.92 

Physical  Properties. 

Fineness  through  a  No.  100  test  sieve  =  94.7  per  cent. 

Fineness  through  a  No.  200  test  sieve  =  76.9  per  cent. 

Boiling  test,  5  hours  =  Good. 

Initial  Set  =  3  hours  and  45  minutes. 

Final  Set  =  6  hours  and  30  minutes- 


36  PORTLAND  CEMENT 

Tensile  strength  I  day  neat  =  383  Ibs. 
Tensile  strength  7  days  neat  =  627  Ibs. 
Tensile  strength  7  days  sand  =  2.13  Ibs. 
Tensile  strength  28  days  neat  =  755  Ibs. 
Tensile  strength  28  days  sand  =  246  Ibs. 

A  number  of  American  Portland  cements  are  quite  low  in 
iron  and  a  few  are  very  high.  There  is  a  very  noticeable 
difference  in  the  color  of  these  extremes.  Color  is  also  due  to 
some  extent  to  the  percentage  of  lime — the  higher  the  lime,  the 
lighter  the  cement. 

Of  late  years  numerous  authorities  have  come  forward  advo- 
cating Portland  cement  containing  high  percentages  of  ferric 
oxide  for  use  in  sea  water,  claiming  for  such  cements  great 
resistance  to  the  disintegrating  influence  of  the  salts  of  mag- 
nesium, etc.,  found  in  sea  water. 

A  cement,  called  "Erz  Cement,"  made  from  a  silicious  lime- 
stone and  iron  ore  is  manufactured  by  the  Krupp  Steel  Co.  at 
Hemmoor,  Germany,  and  is  intended  for  marine  construction. 
It  has  about  the  following  analysis : 

Silica 20.5 

Alumina    1.5 

Iron  oxide n.o 

Lime 63.5 

Magnesia 1.5 

Sulphur  trioxide i  .o 

This  cement  when  mixed  with  plaster  and  exposed  to  the 
action  of  a  concentrated  sea  water,  of  five  times  normal 
strength,  under  a  pressure  of  15  atmospheres  shows  no 
trace  of  expansion  and  contraction.  Ordinary  Portland  cement 
would  be  destroyed  under  such  conditions  in  a  few  days. 

•Eron  cement  shows  high  tensile  and  compressive  strength,  pro- 
vided it  is  very  finely  ground,  otherwise  it  is  very  slow-setting ;  in 
fact  too  slow  setting  for  marine  work.  American  Portland  ce- 
ment containing  over  5  per  cent,  iron  can  be  obtained. 

Replacing  alumina  by  iron  increased  the  specific  gravity  of 
Portland  cement. 


NATURE  AND   COMPOSITION  OF  PORTLAND   CEMENT  37 

Magnesia. 

At  one  time  magnesia  was  considered  dangerous,  now  the 
standard  specifications  allow_4^er_cent.,  and  recent  investigations 
place  the  limit  above  this.  The  popular  supposition  seems  to  be 
that  magnesia  in  considerable  amounts  causes  cement  in  time 
to  expand  and  crack.  Cements  in  which  magnesia  replaces  lime 
are  of  low  tensile  strength  because  magnesium  compounds  have 
only  faint  hydraulic  properties.  A  cement  made  from  magnesite 
and  slate  had  the  following  analysis: 

Silica 27.84 

Iron  oxide  and  alumina 1 1. 16 

Lime ....  2.02 

Magnesia 56.20 

Sulphur  trioxide 1.42 

Loss 0.86 

Briquettes  of  this  cement  gave  at  the  end  of  seven  days  a  neat 
strength  of  31  Ibs.  and  at  the  end  of  one  year  a  strength  of  44 
Ibs.,  each  figure  being  the  average  of  five  briquettes.  Pats  made 
of  this  cement  passed  satisfactory  boiling  and  steam  tests  and 
the  air  and  cold  water  pats  at  the  end  of  two  years  showed  no 
signs  of  expansion  or  cracking.  A  cement  made  of  dolomite 
and  slate  had  about  20  per  cent,  the  strength  of  one  made  of 
pure  limestone  and  slate,  both  cements  being  made  to  agree  with 
the  formula: 

%  magnesia  X  1.4  +  %  lime 
°/o  silica  -[-  alumina  -f-  %  iron  oxide 

DyckerhofF  on  the  other  hand  contends  that  cement  contain- 
ing over  4  per  cent,  magnesia  will  expand  and  crack  in  time  and 
gives  numerous  tests  to  prove  his  conclusions  and  also  cites 
some  instances  of  actual  failure  of  concrete  work  made  with 
cement  high  in  magnesia.  Nearly  all  experimenters  agree  that 
magnesia  in  cement  has  practically  no  hydraulic  value. 

There  are  compounds  of  magnesia  of  great  cementitious  prop- 
erties, however,  one  of  which  is  the  oxychloride  of  magnesia. 
This  compound  forms  the  base  of  Sorel  cement,  which  is  much 
stronger  than  Portland  cement  and  finds  use  in  such  difficult 

1  Tonindustrie-Zeit.,  Feb.  2,  1908,  Cement  Age,  Feb.,  1909. 


38  PORTLAND  CEMENT 

work  as  the  manufacture  of  emery  stones.  It  has  great  powers 
of  endurance  and  is  said  to  withstand  sea  water.  Some  time  ago 
the  author,  acting  upon  the  thought  that  if  calcium  chloride  was 
added  to  cement  this  would  form  an  oxychloride  with  the  mag- 
nesia and  convert  the  latter  from  a  useless  but  necessary  adulter- 
ant into  an  active  cementitious  compound,  took  out  a  patent1 
upon  the  manufacture  of  Portland  cement  from  materials  high  in 
magnesia  by  such  addition  of  calcium  chloride,  the  idea  being 
that  it  would  allow  the  use  of  native  limestones,  which  are  high 
in  magnesia,  with  the  cement-rock.  As  no  amount  of  limestone 
low  in  magnesia  is  found  near  the  Lehigh  cement-rock  and  the 
latter  requires  a  mixture  with  it  of  from  10  to  30  per  cent, 
limestone,  and  as  the  magnesian  limestones  lie  immediately  ad- 
jacent to  the  cement-rock,  the  value  of  the  substitution  of  the 
native  limestone  for  that  coming  from  a  distance  can  be  well 
understood. 

Cement  made  from  cement-rock  and  dolomite  to  which  cal- 
cium chloride  was  added  had  the  following  analysis : 

Per  cent. 

Silica 21.94 

Iron  oxide  and  alumina 10.66 

Lime 55.72 

Magnesia 6.59 

Sulphur  trioxide 0.38 

Chlorine i  .06 

The  clinker  ground  easily  and  when  pulverized  to  the  usual 
fineness  proved  to  have  normal  setting  and  hardening  proper- 
ties and  passed  perfectly  the  steam,  boiling,  cold  water  and  air 
tests  for  soundness.  It  had  the  following  strength  when  tested 
with  three  parts  standard  crushed  quartz-sand. 

7  days 298  Ibs. 

28  days 385  Ibs. 

3  months 426  Ibs. 

6  months 450  Ibs. 

i  year 475  Ibs. 

The  question  of  the  economic  and  satisfactory  manufacture 
of  Portland  cement  from  materials  high  in  magnesia  is  one 
of  great  importance  in  many  parts  of  the  world. 

i  U.  S.  Patent  No.  866,376. 


NATURE  AND   COMPOSITION   OF  PORTLAND   CEMENT  39 

Magnesia  lowers  the  clinkering  temperature  of  the  cement  and 
hence  makes  a  more  fusible  clinker,  and  a  more  easily  burned 
cement.  In  view  of  the  evidence  recently  collected,  it  seems 
safe  to  say  that  magnesia  in  cement  does  not  cause  unsoundness. 
At  the  same  time  it  forms  compounds  of  such  weak  hydraulic 
properties  that  it  may  be  said  to  constitute  an  inactive  sub- 
stance and  consequently  an  adulterant  in  cement  unless  some 
addition,  such  as  calcium  chloride,  is  made  to  the  cement  to 
form  with  it  a  cementitious  compound. 

Whether  magnesia  should  be  considered  in  calculating  cement 
mixtures  is  a  debated  point,  and  .one  with  which  the  hydraulic 
value  of  the  magnesian  compounds  has  nothing  to  do,  as  the 
question  is  simply  whether  or  not  the  magnesia  is  combined  with 
silica  and  alumina  in  cement.  If  it  does  combine,  enough  of  the 
silica  and  alumina  should  be  present,  not  only  to  form  the  proper 
lime  compounds,  but  also  the  proper  magnesian  compound,  or 
else  the  cement  will  be  too  basic  and  will  probably  contain  excess 
of  uncombined  lime. 

(  The  standard  specifications  place  the  maximum  amount  of  mag- 
nesia  (MgO)   allowable  in  a  Portland  cement  at  4  per  cent; 

Alkalies. 

Potash  and  soda  are  present  in  all  cements  in  small  quantities, 
usually  less  than  0.75  per  cent.  A  large  proportion  of  the  alkalies 
present  in  the  raw  material  are  driven  off  in  burning.  Experi- 
ments made  by  the  writer  with  the  cement-rock  of  the  Lehigh 
Valley  indicate  that  at  least  one-half  the  potash  is  lost  in  the 
kiln,  passing  off  in  the  kiln  gases.  The  loss  of  soda  is,  of  course, 
much  less  since  this  is  the  less  volatile  of  the  two  alkalies.  It 
is  supposed  that  the  alkalies  act  as  flux  and  promote  the  combi- 
nation of  the  silica  and  the  alumina  with  the  lime,  and  experi- 
ments made  by  the  writer  with  small  kilns  certainly  confirm  this 
theory.  Several  mills  have  added  soda  ash  in  order  to  make 
the  clinkering  of  their  material  more  easy.  This  practice,  how- 
ever, seems  to  be  of  doubtful  economic  advantage. 

The  addition  of  small  quantities  of  either  the  carbonates  or  the 
hydroxides  of  potash  and  soda  will  cause  cement  to  set  quickly, 


4O  PORTLAND 

and  it  is  probable  that  the  presence  of  any  considerable  quantity 
of  alkali  in  cement  would  cause  it  to  set  quickly.  When  quick- 
setting  cement  is  due  to  the  presence  of  the  alkalies,  the  trouble 
can  be  remedied,  to  some  extent,  by  raising  the  temperature  of 
burning,  thus  volatilizing  the  alkali.  Cements  made  from  alkali 
waste  often  contain  large  quantities  of  potash  and  soda,  in  some 
cases  the  amount  reaching  as  high  as  2.5  per  cent.  Butler1  states 
that  instances  have  occurred  in  which  these  cements  gave  any- 
thing but  satisfactory  results,  and  the  only  fault  that  could  be 
found  with  their  chemical  composition  was  a  slight  excess  of 
alkali.  In  most  cement  the  alkalies  are  present  in  such  small 
quantities  that  their  effects  are  of  little  hydraulic  importance. 

Sulphur. 

Several  compounds  of  sulphur  are  present  in  cement;  chief  of 
these  are  calcium  sulphate  and  calcium  sulphide.  The  action  of 
calcium  sulphate  upon  cement  is  to  delay  the  set.  For  this  reason 
it  is  always  added  in  the  form  of  gypsum  or  plaster  of  Paris  to  the 
cement  after  burning.  The  standard  specifications  so  far  recog- 
nize the  necessity  for  the  addition  as  to  allow  manufacturers  to 
employ  a  proportion  not  exceeding  3  per  cent,  in  order  to  confer 
to  the  cement,  slow-setting  properties.  Although  the  presence  of 
calcium  sulphate  in  small  quantities  is  beneficial  to  cement,  there 
is  no  doubt  that  a  quantity  exceeding  4  or  5  per  cent,  is  injurious. 

The  standard  specifications  allow  1.75  per  cent,  sulphur  tri- 
oxide  (SO3)  in  Portland  cement.  The  retrogression  sometimes 
met  with  in  neat  Portland  cement  briquettes  is  often  attributed 
to  the  presence  of  calcium  sulphate  in  the  cement.  My  own  ex- 
periments, however,  made  with  cements  to  which  no  gypsum 
had  been  added,  and  the  same  cement  with  the  addition  of  2  per 
cent,  gypsum,  do  not  indicate  this,  as,  in  most  cases,  where  re- 
trogression occurred  in  the  cement  to  which  sulphate  had  been 
added,  it  also  occurred  with  the  unsulphated  cement.  Sul- 
phates increase  the  strength  of  cement,  and  if  they  are  present 
in  larger  amounts  than  2  or  3  per  cent,  will  often  cause 
higher  short  time  tests  than  the  long  period  ones,  though  this 

1  Portland  Cements,  t>5'  R.  D.  Butler,  p.  263. 


NATURE  AND   COMPOSITION   OF   PORTLAND  CEMENT  41 

• 

may  be  due  merely  to  the  test  pieces  becoming  brittle.  The  pres- 
ence of  sulphates  in  cement  promotes  soundness,  or  at  least 
enables  some  cements  to  pass  the  accelerated  tests.  The  prop- 
erty of  gypsum  and  plaster  of  Paris  to  retard  the  set  of  cement 
is  touched  upon  to  greater  length  in  the  section  on  "Setting 
Time." 

Carbon  Dioxide  and  Water. 

Carbon  dioxide  and  water  are  present  in  all  cements,  the 
amount  usually  varying  with  the  age  of  the  cement.  Freshly- 
ground  cements  usually  show  less  than  I  per  cent,  of  these  two 
constituents  combined,  while  well-seasoned  ones  may  show  as 
much  as  3  or  4  per  cent.  Under-burned  cements  may,  or  may  not, 
show  high  loss  on  ignition.  It  is  possible  to  drive  off  all  the  car- 
bon dioxide  from  the  raw  material,  and  yet  not  bring  the  mass 
to  the  point  of  incipient  vitri faction  necessary  to  produce  a  sound 
clinker.  Samples  of  under-burned  clinker  will  frequently  show  a 
loss  on  ignition  (water  and  carbon  dioxide)  as  low  as  that  of 
well-burned  cement.  If  the  sample  is  left  in  the  air,  however,  it 
soon  shows  a  very  high  loss  on  ignition,  due  to  absorption  of 
water  and  carbon  dioxide  from  the  air.  Some  of  the  water  pres- 
ent in  cement  can  be  driven  off  at  110°  C,  while  some  of  it  re- 
quires a  red  heat  for  its  expulsion.  Determinations  of  loss  on  ig- 
nition, unless  very  high,  are,  as  a  rule,  of  little  help  in  determin- 
ing the  quality  of  cement,  since  an  amount  as  high  as  4  per  cent, 
may  be  due  to  "aging"  of  the  cement,  which  is  recognized  as 
beneficial  to  it. 

It  is  becoming  the  practice  in  the  United  States  to  season 
clinker  in  the  open  air  in  piles.  This  is  done  to  make  the 
clinker  easier  to  grind.  It  also  allows  harder  burning  because 
such  clinker  can  be  ground  as  easily  after  such  seasoning  as 
a  much  softer  burned  one  without  it.  The  effect,  is  also  to  lower 
the  specific  gravity  by  absorption  of  water  and  carbon  dioxide. 

The  attempt  was  also  made  to  regulate  the  set  of  cement  by 
introducing  steam  into  the  tube  mills  and  so  do  away  with  the 
addition  of  gypsum.  The  attempt  does  not  seem  to  have  been 
successful,  and  at  any  rate  the  practice  has  never  become  general 
with  even  the  mill  which  introduced  it. 


PORTLAND  CEMENT 


Other  Compounds  in  Portland  Cement. 

Besides  the  compounds  mentioned  above,  cement  usually  con- 
tains small  amounts  of  Titanic  acid,  Ti2O3 ;  Ferrous  oxide, 
FeO ;  Manganous  oxide,  MnO ;  Phosphorus  pentoxide,  P2O5 ; 
and  Strontium  oxide,  SrO.  It  is  doubtful  if  these  compounds 
have  any  effect  on  the  hydraulic  or  setting  properties  of  Portland 
cement  when  present  in  the  minute  quantities  usually  found  in 
commercial  cements.  It  is  probable  that  titanic  acid  can  be  sub- 
stituted for  silica,  but  this  cement  would  be  hard  to  burn;  Man- 
ganese oxide  acts  as  a  flux  and  cements  have  been  made  in 
which  Strontium  replaced  lime. 

The  author  found  *'n  three  Portland  cements  from  the  Lehigh 
District  the  amounts  of  the  rarer  constituents  stated  below : 


Cement  No. 

i 

2 

3 

0.28 
0.23 
0.06 
0.08 
0.18 
0.50 
0.26 
0.25 

O.27 

0.16 
0.08 

0.09 
0.48 
0.31 
0.31 

0.32 
O.I  I 
0.09 

0.07 

0-59 
0.38 
0.29 

Potash  •             ....               .          ... 

Soda  

MANUFACTURE. 


Chapter  III. 


RAW  MATERIALS. 


Essential  Elements. 

As  we  have  seen  from  the  preceding  chapter  the  essential  ele- 
ments of  Portland  cement  are  silica,  SiO2,  alumina,  A12O3,  and 
lime,  CaO.  Silica  and  alumina  both  exist  pure  in  nature,  the  first 
as  quartz  and  flint  and  the  second  as  corundum  or  emery.  Neither 
quartz  nor  corundum  are  suitable  for  cement  making,  because 
of  their  extreme  hardness  and  the  impossibility  of  reducing  them 
to  the  degree  of  fineness  necessary  for  their  combining  with  the 
lifne.  Silica  and  alumina,  however,  together  are  the  essentials  of 
clay  (or  shale)  and  this  is  the  source  of  these  elements  for  ce- 
ment manufacture.  Lime  is  not  found  free  in  nature,  but  com- 
bined with  carbon  dioxide  forms  calcium  carbonate,  CaCO3, 
which  occurs  in  many  parts  of  the  country  under  the  names  lime- 
stone, chalk  and  marl.  Most  limestones  contain  some  clay  and 
when  this  is  present  to  the  extent  of  18  or  more  per  cent,  what  is 
known  as  "cement-rock"  or  argillaceous  limestone  results.  Cer- 
tain by-products  of  other  industries  contain  one  or  more  of  the 
essential  elements  of  Portland  cement  in  a  condition,  and  in  pro- 
portions suitable  for  Portland  cement  manufacture.  In  this 
country,  blast-furnace  slag  is  now  used  and  caustic-soda  waste 
has  been  tried. 

Classification  of  Materials. 

Portland  cement  may  be  and  is  manufactured  from  a  variety  of 
raw  materials.  Those  used  may  be  classed  under  two  general 
heads,  (i)  calcareous,  (2)  argillaceous,  according  as  the  lime  or 
the  silica  and  alumina  predominate. 


44  PORTLAND  CEMENT 

Calcareous,  Argillaceous. 

Limestone,  Clay, 

Marl,  Shale, 

Chalk,  Slate, 

Alkali  waste,  Blast-furnace  slag. 
Cement-rock.1 

Any  combination  of  materials  from  these  two  groups  may  be 
used  which  will  give  a  mixture  of  the  proper  composition  for 
burning  (See  Chapter  IV),  but  so  far  the  ones  used  in  this 
country  are: — 

1.  Cement-Rock  and  Limestone. — Used  in  the  Lehigh  Valley 
cement  district  of  Pennsylvania.     This  district  comprises  Berks, 
Lehigh  and  Northampton  Counties  in  Pennsylvania,  and  Warren 
County,  New  Jersey. 

2.  Limestone  and  Shale  or  Clay. — Used  in  many  parts  of  the 
country  as  these  materials  are  widely  distributed. 

j.  Marl  and  Shale  or  Clay. — Used  principally  in  Michigan, 
Ohio,  Indiana  and  Central  New  York. 

4.  B last-Furnace  Slag  and  Limestone. — Plants  are  now  located 
for  the  manufacture  of  cement  from  these  materials  in  Illinois, 
Ohio,  and  Pennsylvania. 

5.  Caustic-Soda  Waste  and  Clay,  formerly  used  by  one  large 
alkali  plant  in  Michigan. 

Table  VIII  shows  the  relative  amounts  of  cement  which  are 
made  from  each  class  of  material.  It  will  be  noticed  that  the 
amounts  made  from  each  group  have  increased  except  that  from 
marl  and  clay. 

Limestone. 

Limestone  is  abundantly  distributed  throughout  the  country 
and  occurs  in  many  geological  periods.  It  consists  essentially  of 
carbonate  of  lime  (calcium  carbonate,  CaCO3,)  and  when  pure 
forms  the  mineral  calcite.  The  principal  foreign  elements  found 
in  limestone  are  silica,  iron  oxide,  alumina,  carbonate  of  magne- 
sia and  the  alkalies,  potash  and  soda.  Limestone  sometimes 
contains  considerable  carbonate  of  magnesia  and  when  this  reach- 

1  Cement-rock  may  be  considered  as  either  calcareous  or  argillaceous.  Usually  it 
may  be  classed  as  the  latter,  but  in  the  neighborhood  of  Nazareth,  Pa.,  the  rock  in  several 
places  runs  so  high  in  lime  as  to  necessitate  the  use  of  slate  or  clay  with  it. 


RAW   MATERIALS 


45 


.i 


5 


X 
to 

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S     CO       r$ 

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s  ^  S 

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Sg  | 

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<  p^    c 

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H 

CO 


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rfr-  ONCO    HH    04    IO  N 

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io  t^.  ci  •-«  co  O 

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VO    —  vo    O 
ON 


t^  O_  ON  iO  ON  "3-  "i  -*CO  CO  vO_ 

of  -^  ioco"  o"  of  joco"  co  jo  o" 


46  PORTLAND  CEMENT 

es  45  per  cent,  of  the  total  carbonates  it  is  known  as  dolomite. 

To  be  suitable  for  Portland  cement  manufacture,  limestone 
should  contain  only  a  little  carbonate  of  magnesia,  5  per  cent  being 
about  the  limit.  Where  the  limestone  is  to  be  used  with  shale 
low  in  magnesia,  6  per  cent,  is  allowable,  or  in  other  words  the 
amount  of  carbonate  of  magnesia  in  the  limestone  should  not  be 
high  enough  to  cause  the  magnesia  in  the  finished  cement  to  be 
more  than  4  per  cent.  This  means  not  above  5^4  per  cent,  of 
carbonate  of  magnesia  in  the  mixture  of  limestone  and  shale  (or 
clay) . 

Where  the  limestone  contains  only  a  few  per  cent,  of  silica, 
alumina  and  iron  oxide  no  attention  need  be  paid  to  the  relative 
proportions  of  these  latter;  but  where  the  limestone  contains 
a  considerable  portion  of  these  constituents  the  relation  between 
them  should  be  such  that  the  limestone  will  when  mixed  with  the 
shale  or  clay  give  a  mixture  in  which  the  silica  and  alumina 
exist  in  the  proper  ratio.  The  amount  of  ferric  oxide  in  the 
limestone  should  not  be  so  high  as  to  cause  the  amount  of  ferric 
oxide  in  the  cement  to  exceed  4  per  cent. 

Limestones  containing  considerable  percentages  of  sulphur, 
say  5  or  6  per  cent.,  have  been  successfully  employed  for  cement 
manufacture.  Most  of  this  sulphur  is  expelled  in  the  kiln. 
There  are  a  number  of  limestone  deposits  through  which  run 
small  seams  of  gypsum,,  notably  those  of  Yankton,  S.  D.  and 
Portland,  Colo.  These  limestones  are  used  for  the  manufacture 
of  Portland  cement  and  the  product  does  not  contain  more  sulphur 
than  is  allowed  by  the  specifications.  The  silica  combines  with  the 
lime,  setting  free  the  sulphuric  acid,  which  latter  is  driven  off  by 
the  high  temperature  of  the  kiln.  Limestones  should  be  free  from 
quartz,  either  in  the  form  of  sand  or  flint  pebbles.  Occasionally 
veins  of  quartz  appear  in  the  stone  and  these  may  be  sorted  out 
in  quarrying. 

In  determining  the  suitability  of  a  limestone  to  be  used  in  the 
manufacture  of  cement,  it  is  always  necessary  to  take  into  con- 
sideration the  shale  or  clay  which  is  to  be  used  with  it,  as  in 
every  case  it  is  the  mixture  of  the  two,  made  in  proper  pro- 


RAW   MATERIALS  47 

portions,  which  must  have  the  right  composition  and  a  shale 
which  contains  a  low  percentage  of  alumina  may  very  often  be 
used  with  a  limestone  containing  a  high  percentage  of  this 
latter  constituent,  etc.  By  calculating  the  composition  of  a 
proper  mixture  of  the  limestone  under  examination  and  the  shale 
to  be  used  with  it,  and  then  from  the  calculated  analysis  of  the 
mixture  determining  the  ratio  between  the  silica  and  alumina, 
as  well  as  ascertaining  the  percentage  of  magnesia,  and  iron 
oxide,  the  suitability  of  the  limestone  and  shale  may  be  deter- 
mined. Directions  for  making  these  calculations  will  be  found 
in  the  next  chapter. 

Since  the  limestone  must  be  reduced  to  a  fine  powder  in  order 
to  intimately  mix  with  the  clay  or  shale  used  with  it,  its  hardness 
is  to  some  extent  a  factor  in  determining  its  suitability  for  ce- 
ment making,  although  improved  forms  of  grinding  machinery 
have  done  much  to  equalize  all  classes  of  material.  As  a  usual  thing 
pure  limestone  is  very  much  harder  than  the  impure  clayey  ones, 
consequently  the  less  pure  limestones  are  really  much  better  for 
cement  manufacture  than  the  hard,  pure  ones.  The  greatest 
factor  in  the  making  of  a  sound  cement  is  the  fine  grinding  of  the 
raw  materials.  Indeed  some  plants  using  limestone  and  clay  have 
found  the  grinding  of  the  mixture  to  the  degree  of  fineness 
necessary  to  give  the  cement  a  good  hot  test,  when  fresh,  a  very 
difficult  proposition.  Some  of  them  have  found  it  preferable  on  the 
score  of  economy  not  to  make  their  fresh  cement  pass  the  sound- 
ness test,  but  to  let  it  season  sound  in  their  bins.  Such  cement 
provided  it  has  seasoned  sound  is  as  good  as  any  and  there 
should  be  no  prejudice  against  its  use. 

In  South  Dakota  and  in  Alabama  there  are  found  certain 
rotten  limestones  or  chalks,  more  or  less  impure  in  composition 
and  easily  ground.  The  former  deposit  has  been  used  for  some 
time  and  the  latter  has  been  lately  utilized  for  Portland  cement 
manufacture.  The  ease  with  which  these  chalks  or  rotten  lime- 
stones can  be  ground  is  a  decided  point  to  their  advantage,  and 
makes  them  most  valuable  raw  materials. 

Table  XI  gives  the  analyses  of  some  limestones  used  for  Port- 


48  PORTLAND 

land  cement  manufacture,  together  with  analyses  of  the  clays 
or  shales  employed  with  them. 

Cement-Rock. 

The  impure  clayey  limestone,  used  for  the  manufacture  of 
Portland  cement  in  the  Lehigh  District,  is  known  technically 
as  "cement-rock."  This  rock  forms  a  narrow  belt  extending  in 
a  northeasterly  direction  from  Reading,  Pa.,  to  a  few  miles  north 
of  Stewartsville,  N.  J.  It  passes  through  the  counties  of  Berks, 
Lehigh  and  Northampton,  in  Pennsylvania,  and  Warren  County, 
New  Jersey,  and  is  about  fifty  miles  long  and  not  over  four  miles 
at  its  greatest  width.  There  were  in  July,  1910,  located  in  this 
district  seventeen  Portland  cement  companies  in  active  operation 
and  one  in  process  of  construction.  The  mills  of  this  district 
produced  in  1908  over  40  per  cent,  of  the  output  of  the  country. 

It  has  been  found  by  experience  that  a  mixture  containing 
about  75  per  cent,  carbonate  of  lime  and  18-20  per  cent,  of  clayey 
matter  (silica,  iron  oxide  and  alumina)  gives  the  best  Portland 
cement,  and  the  impure  limestones  found  in  the  Lehigh  Valley 
approach  more  or  less  nearly  this  composition.  When  this  ce- 
ment1rock  contains  less  than  75  per  cent,  carbonate  of  lime  it  is 
the  practice  here  to  add  sufficient  purer  limestone  to  make  the 
mixture  of  this  proportion.  At  several  mills  around  Nazareth 
and  at  Martins  Creek,  Pa.,  the  rock  contains  more  than  75  per 
cent,  carbonate  of  lime  and  here  instead  of  adding  limestone  it 
is  necessary  to  add  a  little  slate  or  clay  or  cement-rock  low  in  lime 
to  lower  the  percentage  of  lime. 

Geologically  this  cement-rock  is  Trenton  limestone  of  the  low- 
er Silurian  age,  and  lies  between  the  Hudson  shales  and  the  Kit- 
tatinny  magnesian  limestone.  The  upper  beds  of  the  cement- 
rock,  where  it  comes  in  contact  with  the  slate,  are  more  or  less 
shaley  in  composition  and  slatey  in  appearance  and  fracture. 
Often  here  the  rock  contains  less  than  50  per  cent,  carbonate  of 
lime  and  is  not  suited  for  economic  reasons  to  the  manufacture 
of  Portland  cement.  As  we  go  lower  in  the  formation  the  lime 
increases  until  near  the  base  of  the  formation,  in  contact  with 
the  Kittatinny  limestone  it  may  carry  as  high  as  95  per  cent. 


RAW   MATERIALS  49 

carbonate  of  lime.  It  is  from  these  lower  beds  that  the  lime- 
stone necessary  for  mixing  with  the  cement-rock  is  obtained. 
The  Kittatinny  limestone  itself  is  too  high  in  magnesia  (15  to 
20  per  cent.  MgO)  to  use  for  cement  making,  but  there  are 
a  few  beds  in  this  formation  low  enough  in  magnesia  to  use 
successfully.  The  cement-rock  itself  often  carries  5  to  6  per 
cent,  magnesium  carbonate  but  is  never  so  high  in  this  element 
as  the  Kittatinny  limestone.  The  purest  limestone  in  use  in  the 
district  contains  about  98  per  cent,  carbonate  of  lime  and  comes 
from  Annville,  Pa.,  some  50-70  miles  away. 

Cement-rock  is  considerably  softer  than  the  pure  limestones, 
generally  used  with  clay,  consequently  it  is  much  more  easily 
ground.  The  nearer  it  approaches  the  correct  composition  for 
cement  mixture  the  more  valuable  it  is.  In  general,  it  may  be 
said  that  rock  requiring  a  small  admixture  of  clay  will  prove  more 
economical  than  one  requiring  addition  of  limestone  for  a  proper 
mixture ;  since,  in  nearly  every  instance,  the  cement-rock  is  over- 
laid by  clay  which  has  to  be  removed  anyhow,  while  the  lime- 
stone may  have  to  be  bought  or  at  least  quarried.  Equally  desir- 
able is  the  combination  of  a  high  and  a  low  lime  cement-rock. 

The  quantity  of  limestone  added  at  some  of  the  cement  mills  in 
the  Lehigh  District  is  as  much  as  50  per  cent,  of  the  rock  itself, 
and  it  is  no  uncommon  thing  when  limestone  is  bought  to  have 
this  item  alone  cost  from  5  to  10  cents  per  barrel  of  cement  pro- 
duced. A  ton  of  cement-rock  and  limestone  mixture  ready  for 
the  kilns  will  produce  from  3.1  to  3.3  barrels  of  cement.  The 
approximate  quantity  of  limestone  necessary  to  use  with  any  ce- 
ment-rock whose  analysis  is  known,  may  be  found  as  follows : — 

If  the  lime  is  reported  as  carbonate,  CaCO3,  quantity  lime- 
stone necessary. 

75  —  (%  CaCO3  in  cement-rock) 
(%  CaCO3  in  limestone)  —  75 

If  the  lime  is  reported  as  lime,  CaO,  quantity  limestone  nec- 
essary 

42  —  ( %  CaO  in  cement-rock) 


( %  CaO  in  limestone)  —  42 


4 


50. 


PORTLAND  CEMENT 


The  result  in  either  event  will  be  the  number  of  pounds  of 
limestone  it  is  necessary  to  add  to  ioo  pounds  of  cement-rock,  to 
make  a  mixture  of  approximately  correct  composition  for  burn- 
ing. 

In  table  XI  will  be  found  the  analysis  of  some  cement-rocks 
of  the  Lehigh  District  and  also  of  the  limestone  mixed  with  them, 
while  table  IX  gives  a  ve,ry  complete  analysis  made  by  the  author 
of  a  sample  of  rock  of  practically  exact  composition  for  burn- 
ing, used  by  the  Dexter  Portland  Cement  Co.,  Nazareth,  Pa. 
This  is  followed  by  an  equally  complete  analysis  of  a  mixture 
of  Annville  Limestone  and  cement-rock,  used  by  the  Vulcanite 
Portland  Cement  Co.,  Vulcanite,  N.  J.,  made  by  W.  F.  Hille- 
brand,  of  the  U.  S.  Geological  Survey.  This  mixture  is  over- 
clayed,  however,  and  undoubtedly  is  merely  a  chance  sample  and 
not  representative  of  that  company's  usual  practice. 

As  will  be  seen  by  a  reference  to  table  XI,  there  is  consider- 
able difference  in  the  analysis  of  the  various  samples.  Not  only 
is  this  true  between  samples  from  different  quarries  of  the  dis- 
trict but  also  between  samples  from  the  same  quarry.  This  is 

TABIvE  IX. — COMPLETE  ANALYSES  OF  CEMENT-ROCK  AND 
CEMENT-ROCK  LIMESTONE  MIXTURE. 


Cement-rock 

Mixture 

c:r\ 

J7  A  A 

IS  18 

Tin                                                 

O  23 

O  23 

A1  O 

A    ere 

4  Q4 

**l*V?  

o  s6 

O.QS 

o  88 

5~ 

O.46 

j?eg    

0.38 

MnO    

o  06 

o.os 

PaO 

41  8  A 

4O  31 

I  Q4 

4UOA 

i  6s 

No    O 

i.yq. 
O  31 

o  is 

Ko 

O  72 

O  Q7 

P  O 

O  22 

O.2I 

^2^5  

O  33 

Q    

o  7s 

o.  S4 

co  .                                      

32  Q4 

12.38 

Hn   i    TOE:                        

I    SS 

I   31 

HO  •  -  TOG:                                           .  .  .... 

Dried,  sample 

A'OA 

o  38 

100.32 

100.09 

RAW    MATERIALS 


shown  by  table  X,  each  sample  of  which  represents  an  average 
of  ii  drill  holes  16  feet  each. 

TABLE  X. — SHOWING  THE  VARIATIONS  IN  THE  COMPOSITION 
OF  CEMENT-ROCK  FROM  SAME  QUARRY. 


Bench 

Section  of 
bench 

Analyses 

SiOj 

Fe208+Al203 

CaO 

MgO 

First  1  6  feet... 

West  A 

16.26 

7.22 

70.37 

3-95 

First  i6feet... 

WestB 

14.56 

8.64 

72.33 

3-53 

First  1  6  feet... 

Center  C 

16.38 

7.90 

69.59 

3-77 

Second  i6feet. 

West  A 

17-34 

7-94 

67.93 

4.19 

Second  i6feet. 

WestB 

18.94 

6.98 

68.53 

3.9i 

Second  16  feet. 

Center  C 

15-54 

7.10 

71.04 

4.12 

Second  1  6  feet- 

East  D 

17.02 

7.30 

69.34 

4.16 

Second  i6feet. 

East  E 

21.36 

9.OO 

65.41 

3.96 

Third  16  feet.  . 

West  A 

21.98 

8.80 

62.65 

4.87 

Third  16  feet-  . 

WestB 

27.00 

8.10 

69.12 

4-73 

Third  i6feet.. 

Center  C 

16.86 

8.14 

68.54 

5.07 

Third  1  6  feet.. 

EastD 

24.16 

9.14 

60.69 

4-32 

Third  16  feet.. 

EastE 

21.15 

9-5* 

59.09 

4.64 

Fourth  5  feet.. 

Center  C 

25.16 

8.28 

60.42 

4.27 

Marl 

Cement  is  now  made  from  marl  in  Michigan,  Ohio,  New  York, 
and  Northern  Indiana  and  one  plant  is  in  operation  and  one 
under  construction  in  Virginia  to  use  a  shell  marl  of  marine  origin 
and  employ  the  dry  process.  A  considerable  proportion  of  the 
cement  made  in  Michigan  is  made  from  marl  and  clay  or  clay- 
shale. 

Marl  is  more  or  less  pure  carbonate  of  lime,  the  principle  im- 
purities being  clay,  organic  matter  and  carbonate  of  magnesia. 
Marl  beds  usually  occupy  the  bodies  of  ancient  extinct  lakes  or 
else  the  bottoms  and  banks  of  present  ones  and  are  formed  by 
the  precipitation  of  calcium  carbonate  from  water  by  the  agency 
of  certain  algae  or  water  plants.  In  many  instances  the  process 
of  making  marl  beds  is  still  going  on.  Marl  is  soft  and  pulveru- 
lent, sometimes  containing  many  small  shells,  but  usually  the 
larger  part  of  it  passing  a  2OO-mesh  cement  testing  sieve.  It 
therefore  requires  little  grinding  before  burning.  White  marls 
usually  are  free  from  organic  matter,  but  the  grey  marls  often 


52  PORTLAND  CEMENT 

contain  from  5  to  10  per  cent,  of  impurities.  Marl  beds  vary  in 
size  from  a  few  acres  up  to  two  or  three  hundred.  Some  of  the 
companies  in  Michigan  each  have  marl  beds  aggregating  over 
looo  acres  and  measuring  an  average  of  20  feet  deep.  Prof. 
Campbell  has  found  that  a  cubic  foot  of  marl  contains  47.5 
pounds  of  marl  and  generally  about  48  pounds  of  water.  As  ex- 
cavated and  sent  to  the  mill,  however,  it  frequently  contains  much 
more  water  than  the  above  figure. 

Marls  for  use  in  Portland  cement  manufacture  should  possess 
the  chemical  characteristics  outlined  for  limestone  and  in  ad- 
dition be  free  from  sand  and  pebbles.  It  is,  of  course,  possible 
to  separate  the  former  from  marl  by  wash  mills  and  the  latter  by 
specially  designed  screens.  Either  operation  adds  to  the  cost  of 
manufacture,  however.  Some  marls  contain  a  considerable  per- 
centage of  sulphur.  From  experiments  made  by  the  author,  he 
is  inclined  to  think  that  most  of  this  sulphur  is  lost  in  the  kiln. 
If  present  in  the  form  of  iron  pyrites  or  in  combination  with 
organic  matter,  it  is  simply  burned  away.  If  present  as  calcium 
sulphate  it  is  liberated  by  the  combination  of  the  lime  with  the 
silica.  Exactly  how  much  sulphur  is  allowable  the  author  is  not 
prepared  to  say,  but  it  seems  probable  that  at  least  5  or  6  per 
cent.  SO3  might  be  present  without  rendering  the  marl  unfit  for 
the  manufacture  of  Portland  cement.  Johnson1  succeeded  in  mak- 
ing a  sound  true  Portland  cement,  containing  only  1.83  per  cent, 
sulphur,  in  a  small  experimental  kiln  from  a  mixture  of  clay  and 
gypsum. 

Some  marls  are  sticky  and  pasty  in  texture  and  ball  together  as 
clay  does.  Such  marls  are  hard  to  move  from  one  part  of  the 
mill  to  another  and  require  the  addition  of  more  water,  which  has 
subsequently  to  be  evaporated  in  the  kilns,  in  order  to  pump  them 
about. 

The  value  of  a  marl  bed  will  usually  lie  in  its  depth  and 
area  and  physical  characteristics  rather  than  its  chemical  com- 
position. Marl  must,  of  course,  contain  at  least  75  per  cent,  of 
carbonate  of  lime  after  drying  and  deducting  the  organic  matter 

1  Cement  and  Engineering  News,  January,  1905,  p.  n. 


RAW   MATERIALS  53 

and  it  should  not  contain  over  2  or  3  per  cent,  free  silica  (silica 
as  quartz  sand)  nor  more  than  5  per  cent,  carbonate  of  magnesia. 
What  has  been  said  about  the  chemical  requirements  of  lime- 
stone to  be  used  for  the  manufacture  of  Portland  cement  ap- 
plies equally  to  marl.  The  greater  the  depth  of  the  bed  the 
more  economically  it  can  be  worked.  If  the  beds  are  dry  so 
that  the  dry  process  of  manufacture  can  be  employed,  the  value 
of  the  deposit  is  greatly  increased  thereby. 

Usually  marls  require  the  addition  of  about  one-fifth  their 
weight  (when  dry)  of  dry  clay  for  burning.  The  approximate 
proportion  in  a  specifi"  case  may  be  found  as  follows : 

(%  CaO  in  marl)  — 42 

Weight  of  clay  ==  ^-      ,  H    _   ,  .      .      r  X  100. 
42  —  (  %  CaO  in  clay) 

The  result  gives  the  weight  of  clay  (in  pounds)  to  be  added 
to  100  Ibs.  of  marl.  If  in  the  analysis  lime  is  reported  as  carbon- 
ate of  lime,  multiply  this  percentage  by  0.56  for  the  equivalent 
percentage  of  lime,  CaO. 

Table  XI  gives  the  analysis  of  some  marls  used  for  Portland 
cement  making.  (Refer  to  page  63.) 

Clay. 

Clay  consists  of  a  mixture  of  kaolin  with  more  or  less  sand  and 
other  impurities.  Kaolin,  sometimes  called  kaolinite,  is  a  hy- 
drated  silicate  of  alumina,  having  the  symbol  AkC^SiO^HgO. 
Sand  is  composed  of  grains  of  quartz  and  other  minerals.  Clay 
contains  silica  both  as  chemically  combined  silica  in  kaolin  and 
the  other  minerals,  and  in  the  free  state  as  quartz  sand.  Clay  also 
contains  more  or  less  iron  oxide,  lime  and  magnesia  and  smaller 
quantities  of  potash  and  soda.  Clay  originates  from  the  disinte- 
gration of  rocks  containing  minerals  made  up  largely  of  alumina 
and  silica.  The  most  abundantly  occurring  of  these  minerals  are 
the  feldspars,  augite  and  hornblende.  Nephelite  and  sodalite  oc- 
cur also  to  a  much  smaller  extent.  Decomposition  takes  place  by 
the  gradual  leaching  out  of  the  more  soluble  elements  of  the 
minerals  by  water,  leaving  behind  the  less  soluble  ones,  silica  and 
alumina,  together  with  smaller  proportions  of  lime,  magnesia, 
iron,  potash  and  soda.  These  insoluble  portions  are  washed  over 


54  PORTLAND  CEMENT 

and  over  again  and  deposited  in  favorable  places  by  water.  Such 
deposits  are  called  sedimentary  clay,  while  clay  which,  instead  of 
being  washed  away  by  water,  is  left  near  the  rocks  from  whose 
decomposition  it  was  formed  is  called  residual  clay.  The  potter 
deals  more  particularly  with  the  plasticity,  permanence  when 
burnt  and  refractoriness  of  clay,  but  to  the  Portland  cement 
manufacture  these  properties  are  of  very  secondary  importance. 
The  main  thing,  of  course,  is  the  chemical  composition  and  the 
state  of  subdivision  in  which  the  silica  exists.  Roughly  speakng, 
the  clay  should  contain  between  2.5  and  4  times  as  much  silica  as 
alumina.  There  should  also  not  be  more  iron  oxide  than  alumina 
in  the  clay  while  the  best  proportion  between  these  two  is  about 
i  to  3.  Magnesia  and  lime  are  usually  present  only  in  small 
quantities,  the  more  of  the  latter  present  the  better,  but  the  former 
should  be  low,  (not  over  3  or  4  per  cent.).  The  alkalies  should 
not  run  over  3  per  cent.,  as  an  excess  is  likely  to  cause  unsound 
and  quick-setting  cement. 

Most  clays  will  meet  with  the  above  requirements,  the  usual 
point  to  be  looked  into  most  carefully  is  the  condition  of  the  sil- 
ica. All  clay  contains  some  uncombined  silica,  present  as  quartz 
sand  or  pebbles.  The  latter  may  be  separated  from  the  clay  by 
mechanical  means  so  the  former  is  the  one  which  gives  most 
trouble.  The  sand  must  be  present  in  the  clay  in  a  very  finely 
divided  condition.  If  much  (over  5  per  cent.)  is  present  in  the 
form  of  grains  not  passing  a  loo-mesh  sieve,  the  clay  is  unsuited 
to  cement  manufacture.  Under  the  section  on  "Analysis  of 
the  Raw  Materials"  a  method  is  given  for  determining  the  quartz 
sand  failing  to  pass  a  loo-mesh  test  sieve.  Table  XI  gives  the 
analyses  of  clays  used  in  cement  manufacture.  It  should  be  re- 
membered, however,  that  in  considering  the  composition  of  the 
clay,  that  of  the  limestone  must  also  be  considered,  as  the  one 
often  supplements  the  other :  What  is  wanted  is  a  mixture  of 
the  two  of  correct  composition  and  both  may  be  abnormally  pro- 
portioned and  yet  give  this,  the  one  supplying  what  the  other  lacks. 

Shale. 

For  practical  cement  making  purposes  shale  may  be  looked 
upon  as  merely  solidified  clay,  since  the  chemical  composition  of 


RAW   MATERIALS  55 

the  two  are  very  similar  and  the  same  regard  must  be  had  as  to 
the  state  of  subdivision  of  the  free  silica.  Shale  is  preferable  to 
clay  for  mixing  with  limestone  since  segregation  of  the  two  is  less 
likely  to  take  place.  It  also  carries  less  water  and  consequently 
does  not  require  so  much  drying  before  grinding.  Clays  on  the 
other  hand  are  better  suited  to  mixing  with  marls  because  of  the 
similarity  in  physical  properties  between  the  two.  If  a  mixture  of 
dry  clay  and  coarsely  ground  limestone  is  poured  from  a  spout 
into  a  pile  the  clay  will  remain  in  the  center  of  the  pile  and  the 
limestone  will  roll  down  the  sides  of  the  pile.  Now,  if  this  pile 
is  tapped  from  below  in  the  middle,  as  it  would  be  in  a  bin,  the 
first  material  drawn  would  be  most  of  it  clay,  while  the  last  of  it 
would  be  practically  all  limestone.  To  overcome  this  tendency 
to  segregate,  therefore,  it  is  best  to  mix  substances  of  like  physi- 
cal characteristics,  shale  with  limestone  and  clay  with  marl. 

Table  XI  gives  some  analyses  of  shales  used  on  the  manu- 
facture of  Portland  cement. 

TA'BLE  XI. — ANALYSES  OF  MATERIAL  USED  FOR  THE  MANUFACTURE 
OF  PORTLAND  CEMENT  AT  VARIOUS  PLANTS. 
Limestone  and  Clay. 

ALPHA   PORTLAND   CEMENT   Co.,   CATSKILL   PLANT,   CATSKILL,   N.   Y. 
(U.  S.  Geological   Survey  Bui.  No.  243) 

Limestone  Clay 

Silica 1.54  61.92 

Oxide   of    iron    1.04  7.84 

Alumina     0.39  16.58 

Carbonate  of  lime  96.16 

Lime     53.87  2.01 

Carbonate    of    magnesia     1.09 

Magnesia     0.52  1.58 

IRONTON   PORTLAND   CEMENT   Co.,   IRONTON,   OHIO. 
(Analyses  by  W.   P.  Gano) 

Limestone  Shale          Sandstone 

Silica     0.92  54.46  84.62 

Oxide  of  iron    3.70  5.66  2.67 

Alumina    1.16  23.44  7-22 

Carbonate  of  lime    92.78 

Lime    52.00  0.71  0.61 

Carbonate  of  magnesia   0.97 

Magnesia    0.46  i.oo  0.35 

Loss    on    ignition    12.56 


56  PORTLAND 

TABLE  XI. — ( Continued, ) 

MARQUETTE  CEMENT  MANUFACTURING  Co.,  LA  SAU<E,  ILL. 
(Stuart  Smith,  Chemist) 

Limestone  Shale 

Silica    4.20  59.00 

Oxide   of   iron    0.64  2.66 

Alumina 2.11  17-04 

Carbonate   of   lime    90.75 

Lime    50.86  5.51 

Carbonate   of    magnesia    1.84 

Magnesia 0.88  2.80 

Sulphuric  anhydride    0.17  2.10 

Loss  on  ignition    10.60 

THE  HECLA  Co.,  BAY  CITY,  MICH. 
(Arthur  G.  Beck,  Chemist  and  Supt.) 

Alpena  limestone  Clay 

Silica 1.76  46.20 

Oxide   of   iron    0.62  5.57 

Alumina     0.62  16.77 

Carbonate   of   lime    96.06 

Lime    53.83  8.62 

J           Carbonate  of  magnesia   1.51 

Magnesia     .' 0.72  5.22 

Sulphuric    anhydride    0.68 

Loss    on    ignition    13-34 

SECURITY  CEMENT  AND   LIME   Co.,   SECURITY,   MD. 

(From  Maryland  Geological   Survey,   Vol.   VIII) 

Limestone  Shale 

Silica    6.04  62.60 

Oxide    of    iron     0.62  5.23 

Alumina 1.96  21.25 

Carbonate   of   lime    87.25 

Lime     48.88  0.36 

Carbonate  of  magnesia   3.64 

Magnesia   1.74  0.94 

Loss   on   ignition    39-3O 


RAW   MATERIALS  57 

TABLE  XI. — ( Continued. ) 

TIDEWATER   PORTLAND   CEMENT   Co.,   UNION   BRIDGE,  MD. 
(Analyses   by   author) 

Pure  High  silica 

limestone        limestone  Shale 

Silica     0.28             6.40  54.54 

Oxide  of  iron   0.24             0.62  9.80 

Alumina    0.24             0.62  24.24 

Carbonate    of    lime    97-23  9I-I4 

Lime    5449  0.85 

Carbonate    of    magnesia    2.83  1.38 

Magnesia    1.35  1.78 

ALABAMA    PORTLAND   CEMENT    Co.,    DEMOPOLIS,    ALA. 
(Analysis  reported  by  T.  G.  Cairns,  Gen.   Mgr.) 

Chalk 

Silica   9.88 

Oxide  of  iron    6.20 

Alumina    6.20 

Carbonate    of    lime    77-12 

Lime    43-22 

Carbonate    of    magnesia    1.08 

Magnesia    0.52 

Loss   on    ignition    5-72 

ATLANTIC    AND    GULF    PORTLAND    CEMENT    Co.,    RAGLAND,    ALA. 
(C.  N.  Wiley,  Chemist) 

limestone  Shale 

Silica    1.80  63.90 

Oxide  of  iron   0.46  7.68 

Alumina    0.74  21.07 

Carbonate   of   lime    04.66 

Lime   53.03  trace 

Carbonate  of  magnesia   2.24 

Magnesia     1.07  1.52 

Sulphuric    anhydride    none  none 

Loss   on    ignition    * 42-95  4-91 


58  PORTLAND  CEMENT 

TABLE  XI.— (Continued.) 

STANDARD  PORTLAND  CEMENT  Co.,  LEEDS,  ALA. 
(C.    M.   Goodman,    Chemist  and    Supt.) 

lyimestone        Shale          Sandstone 

Silica    2.10  57.11           92.48 

Oxide  of  iron   0.82  7.91              1.69 

Alumina    0.82  20.76             2.69 

Carbonate   of    lime    94-32 

Lime    52.84  2.27              1.50 

Carbonate  of  magnesia   2.92 

Magnesia 1.40  7.90             0.83 

Sulphuric    anhydride     

Loss    on    ignition 42.90  2.16 

TEXAS  PORTLAND  CEMENT  Co.,  CEMENT,  TEXAS. 
(H.  R.  Durbin,  Chemist) 

limestone  Shale 

Silica     6.07  554O 

Oxide   of   iron    2.20  5.45 

Alumina    3.76  22.54 

Carbonate   of   lime    85.48 

Lime , 47.89  3-19 

Carbonate  of  magnesia   1.17 

Magnesia    \ 0.56  0.25 

Sulphuric    anhydride    0.30  1.32 

Sulphur     0.48 

Loss    on    ignition    39.20  9.88 

ST.  Louis  PORTLAND  CEMENT  WORKS,  ST.  Louis,  Mo. 
(John   Taylor,    Manager   and    Chemist) 

limestone  Shale 

Silica    i.oo  56.60 

Oxide   of   iron    0.35  6.00 

Alumina    0.65  20.70 

Carbonate  of   lime    95-OO 

Lime     53-24  i.oo 

Carbonate    of   magnesia    2.00 

Magnesia     0.96  1.75 

Sulphuric    anhydride    0.75 

Loss  on  ignition    11.20 


RAW   MATERIALS  59 

TABLE  XL— (Continued.} 

IOLA  PORTLAND  CEMENT  Co.,  IOLA,  KANS. 

(Analyses  reported  by   H.    Struckmann,   Genl.   Mgr.) 

Limestone  Shale 

Silica    1.16  54.36 

Oxide  of  iron   1.72  7.75 

Alumina     0.58  18.57 

Carbonate  of   lime    92-59                

Lime 51.87  7-44 

Carbonate  of  magnesia  3.36  2.40 

Sulphuric    anhydride    

Loss  on   ignition    43-28  9.76 

UNITED  KANSAS   PORTLAND  CEMENT  Co.,  IOLA,  KANS. 
(E.    C.   Champion,    Chemist  and   Supt.) 

lola  limestone    Concrete  shale 

Silica    2.00  38.62 

Oxide    of    iron    0.92  5.46 

Alumina    0.52  19.20 

Carbonate   of   lime    93-O4  5.77 

Lime    , 52.14 

Carbonate  of  magnesia   3.25 

Magnesia   1.55  1.90 

Sulphuric    anhydride    0.15 

Loss    on    ignition    8.90 

OKLAHOMA  PORTLAND  CEMENT  Co. 
(W.   S.   Creveling,  Chemist) 

limestone  Shale 

Silica    0.42  42.30 

Oxide   of   iron    o.io  5.92 

Alumina  0.71  12.36 

Carbonate  of   lime    98.32 

Lime 55.08  12.86 

Carbonate    of    magnesia    0.59 

Magnesia  0.28  5.50 

Lead   oxide 0.32 

Loss  on  ignition    43-H  18.11 


60  PORTLAND 

TABLE  XI . — ( Continued. ) 

THE   NORTHWESTERN   STATES    PORTLAND   CEMENT  Co.,  MASON   CITY,   lo. 
(Geo.    P.    Diekmann,   Chemist) 

Limestone  Clay 

Silica 1.20  55.60 

Oxide   of   iron    0.32  5.24 

Alumina    0.56  16.39 

Carbonate  of  lime    96.50 

Lime    54.08  6.29 

Carbonate  of  magnesia   i.io  3.04 

Sulphuric    anhydride 1.14 

Loss  on  ignition 1 1.60 

THREE  FORKS  PORTLAND  CEMENT  Co.,  TRIDENT,  MONT. 
(R.  E.  Edelhoff,  Analyst) 

limestone  Cement-rock 

Silica 8.00  16.54 

Oxide-  of    iron    1.16  1.31 

Alumina  3.30  5.37 

Carbonate  of   lime    83.83  72.42 

Lime    46.98  40.59 

Carbonate  of  magnesia   2.87  3.04 

Magnesia  * 1.38  1.46 

Loss    on    ignition    38.69  33.42 

HENRY  Co  WELL  LIME  &  CEMENT  Co.,  COWELL,  CAL. 
(C.  E.  Ktfne,  Chemist) 

Limestone  Clay 

Silica    0.66  55.12 

Oxide  of  iron   0.26  6.20 

Alumina    1.40  20.00 

Carbonate  of  lime   95.40 

Lime   53.47  3.26 

Carbonate   of   magnesia    1.51 

Magnesia    0.72  1.73 

Sulphuric    anhydride    1.64 

Loss  on  ignition 10.70 


RAW   MATERIALS  6l 

TABLE  XI.—  (Continued.} 

PACIFIC  PORTLAND  CEMENT  Co.,  SUISUN,  CAL. 
(U.  S.  Geological  Survey,  Bui.  No.  243) 

Travertine 
limestone  Clay 

Silica    1.21  58.25 

Oxide  of  iron  0.50  7.35 

Alumina     0.70  18.56 

Carbonate   of   lime    95-62 

Lime   53-62  3.10 

Carbonate   of   magnesia    0.92 

Magnesia    0.44  1.28 

Sulphuric  anhydride    o.n  0.45 

Loss  on  ignition    42.98  8.55 

SANTA  CRUZ  PORTLAND  CEMENT  Co.,  DAVENPORT,  CAL. 
(Llewellyn  T.  Bachman,  Chemist) 

L/imestone          Clay  Shale 

Silica    2.03  55.04  65.25 

Oxide  of  iron    0.31  6.12  2.56 

Alumina    1.37  20.72  6.95 

Carbonate    of    lime    94.69 

Lime    53.06  3.08  3.86 

Carbonate  of   magnesia    1.96 

Magnesia 0.95  2.17  0.98 

Sulphuric    anhydride    1.76  1.30 

Loss    on    ignition    41.96  8.64  19-17 

SUPERIOR  PORTLAND  CEMENT  Co.,  CONCRETE,  WASH. 
(Chas.  A.  Newhall,  Chemical  Engineer) 

High  grade     Low  grade 
limestone        limestone  Shale 

Silica    5-o8  11.63            57.36 

Oxide  of  iron 2.28  2.01              8.00 

Alumina    2.28  2.01            16.78 

Carbonate  of  lime   92.50  85.69 

Lime    51-84  5-35 

Carbonate   of   magnesia    0.12  0.66 

Magnesia    0.06  4.11 

Sulphuric    anhydride     trace 

Loss    on    ignition    5-34 


62 


PORTLAND  CEMENT 


TABLE  XI.— ( Continued. ) 
Cement-Rock  and  Limestone. 
ALLENTOWN   PORTLAND  CEMENT   Co.,  EVANSVILLE, 
(Made  by  the  author) 


PA. 


I,ocal  Annville 
Cement-rock    limestone       limestone 

Silica    15.06             2.79  0.36 

Oxide    of    iron    1.30             0.68  0.45 

Alumina    3.60             0.68  0.45 

Carbonate  of  lime   73.64           94.63  97.11 

Lime    41.27 

Carbonate  of  magnesia  3.34              1.80  1.12 

Magnesia    1.60 

DEXTER  PORTLAND  CEMENT  Co.,  NAZARETH,  PA. 
(Made  by  the  author) 

High  lime  L.OW  lime 
cement-rock       cement-rock 

Silica    II. 10  18.15 

Oxide  of   iron    1.24  1.61 

Alumina    4.42  7.21 

Carbonate  of   lime    77.60  68.14 

Lime     43.49 

Carbonate    of    magnesia    4.17  3.88 

Magnesia    1.99  1.86 

EDISON  PORTLAND  CEMENT  Co.,   STEWARTSVILLE,  N.  J. 
(Made  by  the  author) 

Cement-  New  Jersey 

rock  calcite 

Silica    16.16  0.46 

Oxide   of   iron    1.25  0.36 

Alumina     6.98  0.36 

Carbonate  of  lime   70.38  96.60 

Lime   • : 39-44  54-14 

Carbonate    of    magnesia    3.90  3.54 

Magnesia    1.82  1.66 

NORTHAMPTON  PORTLAND  CEMENT  Co.,  STOCKERTOWN,  PA. 
(Made  by  the  author) 

Cement-rock     I^ocal  limestone 

Silica    18.94  3-66 

Oxide   of   iron    1.56  2.10 

Alumina    5.42  2.10 

Carbonate   of   lime    68.53  92.13 

Lime     38.41 

Carbonate  of  magnesia   3.91  2.21 

Magnesia    1.87  1.06 


RAW   MATERIALS  63 

TABLE  XL— (Continued.} 

Marl  and  Clay. 

MICHIGAN  PORTLAND  CEMENT  Co.,  COLDWATER,  MICH. 
(Analyses  by  H.  E.  Brown) 

i Marl >  Cold  water  shale 

Silica    0.15  8.60  57.26  to  61.25 

Oxide  of  iron   0.19  1.54  6.53   "     8.30 

Alumina    0.27  1.30  18.12   "   21.59 

Carbonate   of   lime    54-69  82.51            

Lime    97-52  46.20  1.25    "     1.50 

Carbonate  of  magnesia   .     1.85  5.84  1.49   "     2.31 

Magnesia     0.88  2.78            

Sulphuric  anhydride    0.65    "      1.34 

Organic    matter    0.05  10.50            

Loss  on  ignition  6.19    "      8.32 

WABASH  PORTLAND  CEMENT  Co.,  STROH,  IND. 
(U.  S.  Geological  Survey,  Bui.  No.  243) 

Marl  Clay 

Silica    0.66  57.74 

Oxide  of  iron   0.62  17.76 

Alumina    0.62  17.76 

Carbonate   of    lime    94-91                

Lime  53.17  7-8o 

Carbonate  of  magnesia   0.98               

Magnesia 0.47  3.52 

Sulphuric    anhydride    

Loss  on   ignition    42.35  12.30 

Blast-Furnace  Slag. 

In  1897  the  Clinton  Cement  Co.  in  connection  with  the  Clinton 
Iron  and  Steel  Co.,  erected  a  small  plant  for  the  manufacture  of 
Portland  cement  from  limestone  and  slag,  at  Pittsburg,  and  in 
1900,  the  Illinois  Steel  Co.  began  the  manufacture  of  Portland 
cement  from  blast-furnace  slag-  and  limestone  at  their  South  Chi- 
cago works.  This  company  latter  became  the  Universal  Port- 
land Cement  Co.,  with  works  at  Indiana  Harbor,  Ind.,  South 
Chicago  and  Pittsburg. 

There  are  two  kinds  of  cement  made  from  blast-furnace  slag 
and  the  two  must  not  be  confused,  one  a  true  Portland  made  by 
mixing  limestone  and  slag,  grinding  very  finely  the  resulting  mix- 
ture and  then  burning,  just  as  if  the  raw  materials  were  clay  and 


64  PORTLAND  CEMENT 

limestone  or  cement-rock  and  limestone;  the  other  a  puzzolan  or 
slag  cement  made  by  grinding  with  slaked  lime  suitable  slag, 
which  has  been  previously  chilled  suddenly  by  dropping  into 
water.  The  resulting  mixture  is  then  ready  for  use  and  is  not 
burned. 

At  the  plants  of  the  Universal  Portland  Cement  Co.  the  slag 
is  granulated  by  cooling  it  suddenly  with  water,  dried,  ground, 
and  then  mixed  with  the  proper  proportion  of  ground  limestone. 

Slag  suitable  for  the  manufacture  of  Portland  cement  can  only 
come  from  furnaces  working  on  pure  ores,  such  as  those  of  the 
Lake  Superior  mines,  and  fluxed  with  low  magnesian  limestone. 
Generally  speaking,  the  slag  must  analyze  within  the  following 
limits : 

Silica,  plus  Alumina,  not  over  48  per  cent. 

Iron  and  Alumina,  12  to  14  per  cent. 

Magnesia,  under  3  per  cent. 

There  is  a  slight  thermal  advantage  in  using  slag  for  the  manu- 
facture of  Portland  cement.  The  lime  is  present  as  oxide,  just  as 
it  is  in  cement,  and  no  heat  is  required  to  decompose,  as  is  the 
case  with  limestone  where  heat  is  required  to  change  the  carbon- 
ate to  oxide. 

This  advantage,  however,  is  negatived  to  some  extent  by  the 
necessity  of  driving  off  the  water  used  to  granulate  the  slag.  Even 
were  this  latter  not  the  case,  under  the  present  wasteful  system  of 
burning  cement,  this  saving  would  hardly  be  appreciable. 

Below  is  an  analysis  of  a  typical  slag  used  by  the  Universal 
Portland  Cement  Co.  in  making  their  "Universal"  Portland 
cement. 

Per  cent. 

Silica 33.10 

Iron  oxide  and  alumina 12.60 

Lime 49.98 

Magnesia 2.45 

Alkali  Waste. 

The  precipitated  calcium  carbonate  obtained  from  the  manu- 
facture of  caustic  soda  by  the  Leblanc  process  has  been  used  suc- 
cessfully in  Europe  for  the  manufacture  of  Portland  cement. 


RAW    MATERIALS  65 

The  Michigan  Alkali  Co.,  Wyandotte,  Mich.,  in  1899,  built  a 
small  plant  designed  to  take  care  of  100  tons  of  waste.  This 
plant  has  now  been  leased  to  the  Wyandotte  Portland  Ce- 
ment Co.,  which  uses  limestone  in  place  of  the  alkali  waste  so 
that  the  presumption  is  that  the  process  did  not  pay.  It  seems 
hardly  likely  that  alkali  waste  will  be  used  again  in  this  country 
in  view  of  the  availability  of  much  more  suitable  materials.  Those 
who  are  interested  in  the  process,  however,  will  find  a  paper  of 
some  length  on  the  subject  in  "Cement  and  Engineering  News" 
of  March  and  April,  1900. 

Below  is  an  analysis  of  the  alkali  waste  formerly  used  by  the 
Michigan  Alkali  Co. 

Per  cent. 

Silica 0.60 

Alumina  and  iron  oxide 3.04 

Carbonate  of  lime 95-24 

Carbonate  of  magnesia i.oo 

Alkalies 0.20 

Gypsum. 

Gypsum  either  in  its  native  state  or  after  calcining  is  always 
added  to  Portland  cement  to  regulate  the  set  for  reasons  which 
will  be  explained  in  Chapter  XVI,  and  hence  may  be  consid- 
ered as  one  of  the  raw  materials  of  its  manufacture.  Gypsum 
consists  of  hydrated  sulphate  of  lime,  CaSO4.2H2O.  This  is 
usually  contaminated  by  the  presence  of  more  or  less  silica,  iron 
and  alumina,  carbonates  of  lime  and  magnesia,  organic  matter 
and  sulphides.  Gypsum  is  found  in  many  localities  in  this  coun- 
try and  in  Nova  Scotia  and  New  Brunswick.  From  the  latter 
places  it  is  largely  imported  for  use  in  the  cement  trade,  for 
making  wall  plaster,  plaster  of  Paris,  etc. 

'When  gypsum  is  heated  to  132°  C.  it  loses  three-fourths  of  its 
water  of  crystallization  and  another  hydrate  is  formed  having 
the  formula  (CaSO4)2.H2O  and  commonly  known  as  plaster  of 
Paris  or  calcined  plaster.  If  gypsum  is  heated  to  a  temperature 
of  343°  C.  all  the  water  is  driven  off  and  it  is  converted  to  anhy- 
drite which  has  the  formula  CaSO4,  and  is  known  usually  as  dead 
burned  plasterY 


66 


PORTLAND  CEMENT 


Either  gypsum  or  plaster  of  Paris  may  be  used  to  slow  the  set 
of  cement.  If  the  retarder  is  to  be  added  to  the  clinker  before  the 
latter  is  ground,  gypsum  is  usually  used.  If  the  addition  is  to  be 
made  at  the  stock  house,  when  the  cement  is  being  packed,  finely 
ground  plaster  of  Paris  is  used.  In  valuing  gypsum  or  plaster  of 
Paris  for  cement  manufacture,  the  main  requisite  is  the  quantity 
of  sulphate  of  calcium  or  SO3  it  contains,  and  the  purchaser  has 
to  take  into  consideration  chiefly  how  much  of  this  he  is  getting 
for  his  money.  In  the  case  of  plaster  of  Paris  its  fineness  should 
also  be  taken  account  of,  if  it  is  to  be  added  to  ground  cement. 
The  finer  the  plaster,  the  better  it  is  for  this  purpose. 

A  cement  mill  manufacturing  1,000  barrels  a  day  will  use  about 
4  tons  of  gypsum  or  plaster  per  day.  This  is  usually  purchased 
from  some  dealer  and  arrives  at  the  mill  either  in  bags  or  in 
bulk  the  gypsum  being  crushed  to  pass  an  inch  perforated  screen. 

Below  are  the  analyses  of  some  gypsums  used  in  retarding  the 
set  of  Portland  cement : 

TABLE  XII.— SHOWING  ANALYSIS  OF  SOME  GYPSUMS  USED  IN 
THE  MANUFACTURE  OF  PORTLAND  CEMENT. 


From 

SiO2 

A1208  + 
Fe202 

CaC03 

MgC08 

CaSO4 

H2O 

Nova  Scotia  .  .  • 
Michigan  

O.IO 

^31 

i  18 

0.04 
0.64 

o  i«; 

0.56 
2.27 
o  ^6 

O.I  I 

0.18 

O  «^2 

78.51 
76.83 

?8    O4. 

20.90 
20.01 
IQ.Q8 

New  York  

2.  II 

o  68 

0.61 
o  16 

w»w 

1.18 

0.65 

76.51 
78.08 

ly.ytj 
19.36 
28.14 

The  Valuation  of  Raw  Materials. 

In  passing  on  the  availability  of  raw  material  for  cement  manu- 
facture, a  number  of  things  must  be  considered  besides  mere 
analysis.  The  cost  of  quarrying  or  excavating,  the  power  re- 
quired to  grind  and  the  coal  it  will  take  to  burn  it  must  be  con- 
sidered. With  excavating  we  include  also  cost  of  conveying  to 
the  mill.  Marl  and  clay  are  the  easiest  raw  materials  to  excavate, 
but  on  the  other  hand  the  mill  can  seldom  be  located  near  the  beds 
of  the  former,  owing  to  the  necessity  of  having  the  mill  located 
on  firm  dry  ground.  This  necessitates  pumping  or  carrying  the 
marl,  in  some  instances  several  miles,  and  increases  the  cost  of 
manufacture.  A  very  shallow  marl  bed  can  not  be  worked  as 


RAW    MATERIALS  67 

economically  as  a  deep  one  because  of  the  constant  moving  about 
of  the  excavating  apparatus,  etc.  When  marl  beds  are  located 
in  the  north,  cold  weather  is  apt  to  tie  them  up  by  freezing 
of  the  lake  over  them,  necessitating  either  the  cutting  of  the  ice 
or  the  shutting  down  of  the  mill.  Both  add  to  the  cost  of  produc- 
tion. 

Cement-rock  is  usually  blasted  down,  loaded  on  cars  and 
hauled  by  cable  to  the  mill,  close  at  hand.  It  costs  more  in  pow- 
der and  drilling  than  marl,  but,  if  a  steam  shovel  is  used  to  loacf 
the  cars,  costs  less  after  it  is  down  to  convey  to  the  mill  than 
marl,  as  only  half  as  much  material  has  to  be  handled  owing  to 
the  water  in  the  marl.  Even  when  loaded  by  hand  the  cost  of 
quarrying  cement-rock  is  no  greater  than  for  marl.  A  recent 
estimate1  places  the  cost  of  excavating  marl  at  21  cents  a  ton, 
while  the  writer  knows  of  several  mills  where  the  delivery  of 
cement-rock  to  the  crushers  is  done  at  a  much  smaller  figure  than 
this. 

Limestone  is  harder  than  cement-rock  and  costs  more  to  drill, 
blast  and  break  up  the  lumps  into  sizes  suitable  for  loading  on 
the  cars  or  carts.  Shale  will  cost  about  the  same  as  cement-rock 
to  quarry  and  load,  but  the  mill  is  usually  located  near  the  lime- 
stone deposit  or  marl  beds,  as  much  more  of  these  are  needed, 
consequently  the  shale  must  usually  be  carried  some  distance  to 
the  mill.  The  cost  of  getting  out  either  cement-rock  or  limestone 
will  be  influenced  by  the  amount  of  "stripping"  that  has  to  be 
done.  In  some  mills  this  top  can  be  used,  in  which  case  this  cost 
is  saved. 

Marl  and  clay  are  the  easiest  materials  to  grind,  shale,  cement- 
rock  and  chalky  limestone  come  next,  while  limestone  and  slag 
are  harder  still.  Slag  is  brittle  but  hard,  breaks  up  to  a  size  pass- 
ing a  2O-mesh  sieve  easily,  but  requires  considerable  additional 
grinding  to  make  95  per  cent,  of  it  pass  a  loo-mesh  sieve. 

As  a  general  rule  cement-rock  limestone  mixture  burns  easiest 
of  any  of  the  combinations  in  the  kilns,  limestone-clay,  and  slag- 
limestone  mixtures  are  harder  still  and  the  wet  marl  and  clay 
mixture  requires  much  more  coal  than  any  other.  In  this  case, 

1  Soper — Cement  and  Engineering  News,  Feb..  1894. 


68  PORTLAND 

burning  and  drying  are  considered  together.  Cement-rock  seldom 
contains  more  than  5  per  cent,  moisture  and  limestone  even  less 
as  it  comes  from  the  quarry.  Slag  may  carry  15  or  20  per  cent, 
of  water  left  in  from  the  process  of  granulation,  and  marl  50  to 
60  per  cent.  The  more  intimate  mixture  of  the  argillaceous  and 
calcareous  elements  of  the  cement-rock  limestone  mixture  makes 
it  easier  to  burn  than  the  equally  dry  limestone-clay  combination, 
while  the  large  quantity  of  water  to  be  driven  off.  in  the  kilns 
makes  the  burning  of  the  marl-clay  combination  so  costly.  If 
marl  and  clay  are  introduced  into  the  kiln  dry  they  require  no 
more  fuel  to  burn  than  the  cement-rock-limestone  combination. 
The  subjects  of  burning  and  grinding  are  treated  of  to  greater 
length  in  special  chapters  and  these  should  be  consulted  for  data 
relative  to  the  cost  of  manufacturing  Portland  cement  from 
various  kinds  of  raw  material. 

Portland  cement  can  be  made  from  such  a  variety  of  materials 
that  almost  every  geological  report  will  show  analyses  of  hun- 
dreds of  limestones,  clays,  shales  and  marls  suitable  for  the 
manufacture  of  cement. 

The  mere  fact  therefore  that  raw  materials  of  suitable  chem- 
ical composition  for  the  manufacture  of  Portland  cement  exists 
in  a  certain  locality  is  no  occasion  for  the  erection  of  a  mill  on 
this  site,  because  the  success  of  the  enterprise  will  depend  more 
upon  local  conditions  than  upon  the  raw  materials  themselves. 

The  cost  of  fuel,  labor  and  supplies  must  be  taken  into 
consideration  as  well  as  the  ability  to  market  the  product.  The 
fuel  item  in  the  manufacture  of  Portland  cement  is  a  big  one, 
dry  material  requiring  from  150  to  200  Ibs.,  under  the  usual 
system,  for  burning  and  grinding. 

Portland  cement  is  so  bulky  in  proportion  to  its  value  that  the 
nearness  of  the  mill  to  market  is  one  of  the  most  important 
items. 

The  Lehigh  District  is  blessed  with  a  soft  easily  ground  ce- 
ment-rock, but  it  probably  owes  its  development  also  to  cheap 
coal  and  labor,  experienced  men  and  its  proximity  to  such 
markets  as  New  York,  Philadelphia,  and  Boston. 


Chapter  IV. 


PROPORTIONING  THE  RAW  MATERIALS. 

While  a  glance  at  the  table  of  analysis  on  page  29  will  show 
wide  variation  in  the  chemical  composition  of  Portland  cement, 
it  must  not  be  supposed  that  such  latitude  in  proportioning  the 
raw  materials  really  exists.  If  the  resulting  Portland  cement  is  to 
be  sound,  normal  setting,  and  of  good  strength,  it  is  imperative 
that  the  raw  materials  shall  be  correctly  proportioned,  as  to  the 
balance  between  the  silica  and  alumina  on  the  one  hand  and  the 
lime  on  the  other.  Cements  from  different  mills  often  vary  sev- 
eral per  cent,  from  each  other  as  to  the  silica,  lime  and  alumina, 
and  yet  one  appears  as  good  as  the  other.  This  variation  in 
composition  is  often  due  in  part  to  addition  of  gypsum  to,  and 
the  contamination  by  the  coal  ash  of  the  clinker  and  also  to  the 
absorption  of  carbon  dioxide  from  the  air.  It  is  still,  however, 
evident  that  this  will  not  account  for  all  the  variations,  and  that 
the  raw  mixtures  from  which  cement  is  made  vary  widely,  with- 
in certain  limits,  at  the  different  works. 

Many  attempts  have  been  made  to  put  the  calculation  of  ce- 
ment mixtures  on  a  strictly  scientific  basis.  Considering  as  cor- 
rect the  theories  of  Le  Chatelier  and  Newberry,  that  cement 
was  composed  of  definite  chemical  compounds,  this  was  a  com- 
paratively easy  matter  and  was  merely  a  question  of  molecular 
or  combining  weights.  In  the  present  unsatisfactory  condition 
of  our  knowledge  of  the  composition  of  Portland  cement,  it  is  of 
course  an  impossibility  to  scientifically  express  the  proportions 
of  the  various  elements  in  mathematical  formulas.  If  Portland 
cement  is  a  solid  solution  of  lime  in  ortho-silicates  and  ortho- 
aluminates  of  lime,  it  seems  highly  probable  that  no  mathematical 
formula  can  be  devised,  because  the  solubility  of  the  lime  in  the 
magma  may  be  greatly  increased  or  decreased  by  both  manu- 
facturing conditions  and  the  composition  of  the  magma  itself. 


70  PORTLAND  CEMENT 

The  case  seems  analogous  to  that  of  steel.  Here  phosphorous 
promotes  the  solution  of  carbon,  and  silicon  causes  it  to  separate 
from  the  solution.  The  sudden  quenching  of  steel  has  its  effect 
on  the  physical  properties  of  the  metal  and  similarly  the  sudden 
cooling  of  clinker  by  dropping  it  into  water  not  only  changes 
its  color  but  also  makes  it  slower  setting  and  smoother  trowel- 
ling. The  very  slow  cooling  of  clinker  sometimes  causes  it  to  dust, 
and  cement  made  from  such  clinker  is  always  unsound,  possibly 
because  during  the  slow  cooling  the  lime  dissolved  in  the  magma 
separates  from  the  solution. 

Michaelis1  bases  his  formula  on  the  hydraulic  index,  and  in- 
deed it  may  be  considered  as  the  reciprocal  of  this,  or  the  ratio 
between  the  percentage  of  lime  and  the  combined  percentages 
of  silica,  alumina  and  iron  oxide  present  in  Portland  cement.  He 
states  that  this  ratio  must  lie  within  the  limits  of  I  to  1.8  and  I  to 
2.2,  and  practically  all  American  cements  satisfy  this  formula. 
He  proposes  the  empirical  figure  2.  His  formula  stated  in  the 
form  of  an  equation  is 

%  lime 
%  silica  -j-  %  iron  oxide  -|-  %  alumina 

The  writer  has  found  that  while  this  formula  will  in  some  in- 
stances give  a  mixture  which  would  result,  when  burned,  in  a 
very  much  over-clayed,  underlimed  and  consequently  quick-set- 
ting cement,  still  taken  as  a  whole  it  is  as  satisfactory  as  any  of 
those  formulas  based  on  molecular  weights.  The  fixed  ratio  of 
2  does  not  seem  to  be  applicable  to  all  cases,  though  this  is  prob- 
ably often  due  as  much  to  manufacturing  conditions  as  to  com- 
position of  the  material.  Of  four  cements  analyzed  by  the 
writer,  each  from  a  different  mill,  the  ratios  were:  A.  1.92,  B. 
2.01,  C.  2.07,  D.  2.18.  Any  cement  made  at  mill  D  with  this 
formula  would  have  been  decidedly  quick-setting.  When  the 
contamination  of  the  cement  by  the  fuel  ash  is  taken  into 
consideration  it  is  probable  that  A  is  the  only  one  of  these  four 
cements  in  which  the  ratio  between  the  lime  and  the  silicates  be- 
fore burning  was  2. 

1  Cement  and  Engineering  JVezvs,  August,  1900. 


PROPORTIONING    THE    RAW    MATERIALS  71 

The  writer  has  found  that  in  his  experimental  work,  where 
the  raw  materials  were  ground  to  a  fineness  of  95  per  cent, 
through  a  No.  100  test  sieve,  it  has  always  been  possible  to 
make  a  sound  cement,  of  normal  setting  properties  and  good 
strength  when  the  composition  of  this  cement  met  the  ratio: 

%  lime 
%  silica  —  u/c  iron  oxide  —  %  alumina 

provided  the  ratio  between  the  silica  and  the  alumina  was  not 
less  than  2.5  to  I  nor  more  than  5  to  i. 

In  mill  practice,  however,  it  is  seldom  that  as  high  a  ratio  as 
this  can  be  carried.  Just  what  the  ratio  should  be  depends  upon 
conditions  of  manufacture  and  the  nature  of  the  materials.  When 
the  alumina  is  low,  this  ratio  is  often  carried  as  low  as  1.9  with- 
out obtaining  quick-setting  cement.  On  the  other  liand,  when 
the  alumina  is  high,  it  is  often,  but  not  always,  necessary  to  carry 
the  ratio  as  high  as  2.05  to  avoid  quick-setting  cement. 

The  formula  used  to  proportion  the  raw  materials  so  as  to 
give  a  cement  having  a  ratio  of  2.05  is  as  follows : 

Limestone  (or  marl) 
Clay  (or  shale  or  cement-rock) 

( %  Si02  +  ^Fe203  +  % A1203  in  clay)  X  *X  —  ( %  CaO  in  clay) 
(CaO  in  limestone)  —  (%  SiO2  +  %  Fe2O,  -f  ^A12O3  in  limestone)  X  «X  ' 

The  additional  0.2  added  in  the  formula  is  to  take  care  of  the 
small  amount  of  coal  ash  which  enters  the  cement. 

If  in  the  analysis,  the  lime  is  given  as  carbonate  of  lime,  2% 
becomes  4,  for  CaO  :  CaCO  : :  56  :  100  : :  2j4  :  4. 

As  an  example  of  the  use  of  the  formula  suppose  we  wish  to 
calculate  the  proper  mixture  of  cement-rock  and  limestone  of 
the  following  analyses. 

ANALYSES. 

Cement-rock  limestone 

Silica 19.06  2.14 

Iron  oxide 1 .14  0.46 

Alumina 4.44  i.oo 

Carbonate  of  lime 69.24  94-35 

Carbonate  of  magnesia 4.21  2.18 


72  PORTLAND 

The  calculation  is  as  follows : 

Limestone          (19.06-]-  1-14  +  4-44)  X  4 — 69.24 29.32 

Cement-rock     94.35  —  (2.14  -f  0.46+  i.oo)  X  4        79-95 

Or  for  100  part  cement -rock  there  will  be  required 

29.32  X  ioo  v 

=  16.7  parts  limestone. 

79-95 

Newberry  followed  up  his  paper  on  the  constitution  of  Port- 
land cement,  mentioned  in  Chapter  II,  with  the  first  formula, 
based  on  scientific  rather  than  empirical  knowledge,  of  which 
the  writer  knows.  Considering  cement  to  be  composed  of  tri- 
calcium  silicate,  3CaO.SiO2,  containing  2.8  times  as  much  lime 
as  silica,  and  dicalcium  aluminate,  2CaO.Al2O3,  containing  i.i 
times  as  much  lime  as  alumina,  he  proposed  the  following: 

Lime  —  silica  X  2.8  +  alumina  X  i.i. 
Carbonate  of  Lime  =  silica  X  5.  +  alumina  X^. 

As  this  formula  represents  the  maximum  of  lime  which  a  ce- 
ment could  carry,  if  it  were  manufactured  under  ideal  conditions 
as  to  grinding  and  burning,  conditions  which  are  never  met  with 
in  practice,  he  found  it  necessary  in  actual  work  to  carry  the 
lime  a  little  lower  than  called  for  by  the  formula,  say  between 
95  and  98  per  cent,  of  the  maximum.  Ninety-five  per  cent,  of 
the  maximum  would  give  the  following: 

Carbonate  of  lime  =  silica  X  4-8  +  alumina  X  1.9. 

Newberry's  formula  would  make  a  cement  containing  23  per 
cent,  silica  and  6  per  cent,  alumina  contain  (23  X  2.8  -f-  6  X  i.i) 
X  0.9  =  63.9  and  one  containing  21  per  cent,  silica  and  8  per 
cent,  alumina  contain  (21  X  2.8  -}-  &  X  i.i)  X  0.9  =  60.8.  As 
a  matter  of  fact  there  is  no  such  difference  between  high  silica 
and  high  alumina  cements,  as  table  VII  will  show. 

As  an  example  of  the  method  of  using  the  formula  let  us  sup- 
pose we  wish  to  make  a  cement  mixture  from  limestone  and  ce- 
ment-rock of  the  composition  given  in  the  preceding  example. 

The  calculation  is  as  follows : 


PROPORTIONING    THE    RAW    MATERIALS  73 

LIMESTONE. 

Total  carbonate  of  lime 94-35 

Silica 2.14  X  4-8  =  10.27 

Alumina    1.00X1.9=    I-9° 

12.17 


Available  carbonate  of  lime  in  100  parts 82. 18 

CKMENT-ROCK. 

Silica 19-06  X  4-8  =  91.49 

Alumina 4.44X1.9=    8.44 

99-93 

Less  carbonate  of  lime  contained 69.24 

Required  carbonate  of  lime  for  100  parts 30.69 

The  number  of  parts  of  limestone  required  for  100  parts  ce- 
ment-rock will  then  be 

30.69  X  IPO  = 
82.18 

37.3  Ibs.  limestone  contain 35. 19  Ibs.  CaCOs 

100.0  Ibs.  cement-rock  contain 69.24  Ibs.  CaCO, 

137.3  Ibs.  mixture 104.43  Ibs.  CaCOs 

Mixture  should,  therefore,  analyze: 

104.43  X  ioo  ^  carbonate  of  lime. 

137-3 

A  table1  for  saving  the  multiplication  in  calculations  by  this 
and  other  formulas  when  the  percentages  are  to  be  multiplied  by 
a  fixed  sum  is  shown  in  Fig.  2.  It  is  to  be  employed  when  New- 
berry's  formula  is  used  but  the  principle  is  the  same  and  it  will 
serve  to  illustrate  this  graphic  method  of  calculation  no  matter 
what  formula  is  employed.  It  is  made  of  cross-section  or  co- 
ordinate paper,  such  as  can  be  bought  by  the  sheet  or  yard  from 
any  dealer  in  draughtsman's  supplies.  The  paper  ruled  in  squares 
every  centimeter  with  broad  lines  and  these  spaces  divided  again 
into  tenths  by  fine  lines  is  best  for  this  use.  A  sheet  of  this  of 
sufficient  size  to  cover  all  raw  material  used  in  the  particular 
plant  is  either  pasted  to  sheet  of  stiff  card  board  or  tacked  to  a 
drawing  board.  After  drying,  the  large  divisions  on  the  lower 

1  Meade— Cement  and  Engineering  News,  December,  1901. 


74 


PORTLAND  CEMENT 


margin  are  numbered  i,  2,  3,  etc.,  to  correspond  to  the  percent- 
ages of  silica  and  alumina  in  the  clay,  while  the  divisions  of  the 
same  size  on  the  right  and  left  hand  margins  are  numbered  5, 
10,  15,  etc.,  to  correspond  to  pounds  of  calcium  carbonate.  Now 
two  lines  are  drawn,  one  making  an  angle  of  45°  with  the! 


&ii 


80 


X 


-J 


60 


9 


*y 


O 


**$ 


Fig.  2.— Graphic  method  of  proportioning  cement  raw  materials. 

horizontal  margin  and  passing  through  the  o,  o  point,  the  other 
passing  through  the  same  o,  o  point  but  making  an  angle  of 
21°,  48'.  The  first  line  represents  the  "calcium  carbonate-silica" 
ratio  and  should  be  so  designated,  the  second  the  "calcium-carbon- 
ate-alumina" ratio.  The  abscissas  (figures  on  the  lower  mar- 
gin) of  points  on  the  calcium  carbonate-alumina  line  represent 


PROPORTIONING    THE    RAW    MATERIALS  75 

the  percentage  of  silica  in  the  cement-rock  and  the  ordinates 
(figures  on  the  side  margins)  the  corresponding  weight  of 
calcium  carbonate.  Similarly  the  abscissas  of  points  on  the 
calcium  carbonate-alumina  line  express  the  percentage  of  alumina 
and  the  ordinates  of  these  points  the  corresponding  weight  of 
calcium  carbonate.  As  an  example,  to  explain  the  use  of  the 
table,  suppose  we  wish  to  know  how  much  calcium  carbonate 
to  mix  with  a  rock  of  the  composition : 

Per  cent. 

Silica 18.0 

Alumina,  etc 8.3 

Calcium  carbonate 67.3 

Other  constituents 5.9 

100.0 

First  find  the  calcium  carbonate  equivalent  to  the  silica  in  the 
stone.  To  do  this  run  up  the  vertical  line  corresponding  to  18 
to  "c"  where  it  cuts  the  line  marked  "calcium  carbonate  silica." 
The  ordinate  "b"  of  this  point,  (found  by  running  along  the 
nearest  horizontal  line  to  "c"  to  the  margin)  or  90,  will  be  the 
weight  of  calcium  carbonate  equivalent  to  the  silica.  Next  find 
the  calcium  required  for  the  alumina  by  running  up  the  vertical 
line  corresponding  to  8.3  to  "d"  where  it  cuts  the  line  marked 
"calcium  carbonate-alumina"  and  then  along  the  nearest  hori- 
zontal line  to  this  point  to  the  side  margin.  The  reading  here 
"e"  or  1 6.6  will  be  the  weight  of  calcium  carbonate  required 
for  the  alumina.  The  silica  and  alumina  together  of  course  will 
require  16.6  +  9°  or  106.6  pounds  of  calcium  carbonate,  but 
since  the  cement-rock  contains  67.3  per  cent,  calcium  carbonate 
it  is  only  necessary  to  add  to  it  106.6 — 67.3  or  39.3  pounds  of 
calcium  carbonate. 

It  is  not  necessary  to  use  a  protractor  in  drawing  the  "calcium 
carbonate-alumina"  and  the  "calcium  carbonate-silica"  lines.  It 
is  evident  that  both  lines  must  pass  through  the  o,  o  point.  Any 
other  point  through  which  they  must  pass  may  be  quickly  found 
by  calculation  and  the  lines  drawn  through  these  two  points.  For 
example  25  per  cent,  silica  will  require  25  X  5  or  125  pounds  of 
calcium  carbonate.  So  if  the  line  "calcium  carbonate-silica"  is 


76  PORTLAND  CEMENT 

drawn  through  the  o,  o  point  and  the  point  of  intersection  be- 
tween the  vertical  line  corresponding1  to  25  per  cent,  silica  and 
the  horizontal  line  corresponding  to  125  pounds  of  calcium 
carbonate,  it  will  have  the  proper  angle.  Similarly  the  alumina 
line  should  be  drawn  through  the  o,  o  point  and  that  of  the 
intersection  of  the  vertical  line  corresponding  to  25  per  cent, 
alumina  and  the  horizontal  line  corresponding  to  25  X  2  or  50 
Ibs.  of  calcium  carbonate. 

The  substitution  of  any  other  lime-silica  and  alumina  ratio  than 
that  represented  by  Newberry's  formula  can  easily  be  effected. 
For  example  let  us  suppose  that  in  a  given  plant  Newberry's  for- 
mula gives  an  "overlimed"  cement,  and  that  a  formula 

Calcium  carbonate=%  silicaX4-9+%  alumina X 1-96 
gives  better  results.  Then  in  order  to  express  this  ratio  it  is  nec- 
essary to  draw  the  silica  line  through  the  o,  o  point  and  the 
point  of  intersection  of  the  vertical  line  representing  25%  silica 
and  the  horizontal  line  representing  25  X  4-9  or  122.5  pounds  cal- 
cium carbonate.  The  alumina  line  is  drawn  through  the  o,  o 
point  and  that  of  the  intersection  of  the  vertical  line  representing 
25%  alumina  and  of  the  horizontal  line  25  X  1.96  or  49.0  pounds 
calcium  carbonate. 

Nothing  will  be  gained  by  having  the  larger  divisions  of  the 
co-ordinate  paper  represent  less  than  one  per  cent,  silica  or 
alumina  and  five  pounds  of  calcium  carbonate,  since  the  small 
spaces  will  then  represent  o.i  per  cent,  and  technical  determina- 
tions of  lime,  silica  and  alumina  are  seldom  nearer  the  truth  than 
this.  This  will  keep  the  tables  well  down  in  size.  When  used 
with  clays  high  in  silica  space  can  be  saved  by  having  two  tables — 
one  ranging  say  from  10-25%  and  serving  for  the  alumina  in  the 
clay  and  the  alumina  and  silica  in  the  marl,  the  other  ranging  say 
from  45  to  60%  for  the  silica  in  the  clay.  In  these  tables  two 
points  must  of  course  be  determined.  In  the  first  the  silica  line 
would  of  course  pass  through  the  point  of  intersection  of  the  ver- 
tical and  horizontal  lines  representing  10%  silica  and  10  X  5  or  50 
pounds  calcium  carbonate,  respectively,  and  the  point  of  intersec- 
tion of  the  vertical  and  horizontal  lines  representing  25%  silica 


PROPORTIONING    THE)    RAW    MATERIALS 


77 


and  25X5  or  125  pounds  of  calcium  carbonate,  respectively.  While 
in  the  second  table  it  would  pass  through  the  points  of  intersection 
of  the  vertical  line  representing  45%  silica  and  the  horizontal 
line  representing  45X5  or  225  pounds  of  calcium  carbonate,  and 
of  the  vertical  line  corresponding  to  60%  silica  and  the  horizontal 
line  corresponding  to  60X5  or  300  pounds  calcium  carbonate. 

The  lines  may  of  course  be  drawn  to  represent  the  lime,  cal- 
cium oxide,  required;  in  which  event  the  main  vertical  divisions 


Fijf .  3.— Graphic  method  for  calculating  limestone, 

should  be  numbered  2,  4,  etc.,  and  have  twice  the  value  of  the 
space  on  the  horizontal  margin.  The  silica  line  would  in  this 
event  be  drawn  through  the  O,  O  point  and  the  point  of  intersec- 
tion of  the  vertical  line  corresponding  to  25%  silica  and  the  hori- 
zontal line  corresponding  to  25X2.8  or  70  pounds  calcium  oxide. 
The  above  table  shows  us  merely  the  amount  of  pure  carbon- 
ate of  lime  required  by  the  cement-rock  clay  or  shale.  To  find 
the  limestone  required  it  is  of  course  necessary  to  find  the  avail- 
able carbonate  of  lime  it  contains  by  the  above  chart  and  then 


78  PORTLAND  CEMENT 

calculate  the  quantity  to  be  added  as  shown  on  page  54.  The 
following  table,  Fig.  3,  will  save  this  calculation  also,  however. 
A  large  piece  of  co-ordinate  paper  is  fastened  to  a  board  and  the 
main  divisions  of  the  lower  margin  are  numbered  10,  20,  30,  40* 
etc.,  to  correspond  to  pounds  of  limestone.  Those  on  the  right 
and  left  hand  margins  are  numbered  10,  20,  30,  40,  etc.,  and  rep- 
resent pounds  of  calcium  carbonate  required  for  the  cement-rock. 
On  the  vertical  line  100,  the  main  divisions  are  numbered  10,  20, 
30,  etc.,  to  represent  pound  per  100  or  percentage  of  available 
calcium  carbonate  in  the  limestone.  A  ruler  is  fixed  so  as  to  turn 
about  the  o,  o  point.  The  pivot  around  which  the  rule  moves 
must  be  on  a  line  with  the  edge  of  the  ruler.  It  is  only  neces- 
sary to  set  the  edge  of  the  ruler  at  the  point  on  the  100  vertical 
line  (This  line  is  in  the  drawing  made  broad  but  it  would  be  bet- 
ter to  rule  over  it  or  to  one  side  in  red  ink.)  representing  the  per- 
centage of  available  calcium  carbonate  in  the  limestone.  The  edge 
of  the  ruler  is  then  used  as  if  it  were  a  diagonal  line. 

To  find  the  number  of  pounds  of  limestone  equivalent  to  a 
given  weight  of  calcium  carbonate,  glance  along  the  horizontal 
line  corresponding  to  the  quantity  of  pure  calcium  carbonate  re- 
quired until  it  meets  the  ruler's  lower  edge.  The  corresponding 
reading  at  the  lower  margin  will  give  the  weight  of  limestone. 
For  example,  using  the  table,  we  wish  to  know  how  much  of  a 
limestone  containing  32.5  pounds  available  CaCO3  is  required  for 
a  cement-rock  that  requires  39.3  pounds  calcium  carbonate.  Set 
the  ruler's  lozver  edge  so  it  intersects  the  100  vertical  line  at  32.5 
and  run  the  eye  along  the  horizontal  line  corresponding  to  39.3 
to  where  it  cuts  the  diagonal  line  which  passes  the  100  vertical 
line  at  32  (or  33),  and  then  down  the  nearest  vertical  line  to  the 
margin,  the  reading  here,  or  121,  will  be  the  weight  of  limestone 
needed. 

Fixed  Lime  Standard. 

While  the  above  formulas  are  employed  very  frequently 
for  calculating  cement  mixtures  from  complete  analysis,  as  in 
making  laboratory  trial  burnings,  or  when  starting  up  a  new 
mill,  or  opening  a  new  deposit,  it  will  be  found  more  practicable 


PROPORTIONING    THE)    RAW    MATERIALS  79 

in  actual  mill  routine  work,  to  fix  upon  a  certain  percentage 
of  carbonate  of  lime  found  to  give  satisfactory  results  by  ex- 
perience and  to  keep  the  mixture  as  near  this  as  possible.  Pro- 
vided the  amount  of  water,  organic  matter  and  magnesia  is 
constant  in  raw  materials,  it  will  be  comparatively  easy  to  keep 
a  pretty  uniform  mixture  by  merely  watching  the  percentage 
of  carbonate  of  lime.  In  the  cement-rock  limestone  mixtures  of 
the  Lehigh  District  the  conditions  are  pretty  constant  and  it  is 
the  usual  practice  here  to  "control  the  mix"  by  keeping  the  per- 
centage of  carbonate  of  lime  in  it  around  a  fixed  point  (usually 
74.5  to  75.5)  the  standard  varying  at  different  mills.  In  most 
mills  using  limestone-clay  mixtures,  very  much  the  same  con- 
ditions obtain,  the  magnesia  and  water  remaining  fairly  con- 
stant and  organic  matter  being  present  only  in  very  small  per- 
centages. Some  clays  show  considerable  variations  in  different 
parts  of  the  bed  in  the  relative  proportions  of  the  silica  and  the 
alumina  to  each  ether.  In  this  event,  the  clay  should  be  so 
wdrked  as  to  give  a  constant  ratio  between  the  silica  and  the 
alumina.  By  doing  this  a  constant  lime  standard  may  be  held  to 
and  a  cement  of  more  uniform  setting  properties  will  result.  In 
the  marl-clay  mixtures  water  and  organic  matter  are  apt  to  vary 
widely  and  in  order  to  make  a  uniform  mix  it  is  necessary  to  do 
more  than  merely  determine  the  lime  in  the  slurry,  as  the  wet 
mixture  of  marl  and  clay  is  called.  When  the  organic  matter  is 
constant  it  is  merely  necessary  to  dry  the  mixture  and  determine 
the  carbonate  of  lime  as  in  a  limestone  cement-rock  or  limestone- 
clay  mixture.  In  controlling  the  mixture  by  a  carbonate  of  lime 
determination  it  is  necessary  that  the  ratio  between  the  silica  and 
alumina  be  kept  constant,  this  can  usually  be  done  without  diffi- 
culty after  a  thorough  prospecting  of  the  raw  materials.  This 
problem  will  usually  be  simplified  by  having  the  quarrying  opera- 
tions spread  out  over  the  whole  face,  and  on  several  ledges,  and 
not  confined  to  one  particular  spot.  For  instance,  suppose  a 
quarry  to  have  a  face  of  100  ft.  and  a  depth  of  48  ft.  and  to  be 
worked  in  benches  of  16  ft.  each.  It  will  be  a  simpler  matter  to 
keep  a  constant  ratio  between  the  silica  and  the  alumina  by  dis- 


8O  PORTLAND 

tributing  the  quarry  force  over  the  whole  face  taking  rock  from 
several  benches  than  it  would  be  by  localizing  the  work  with  a 
steam  shovel  at  one  point. 

Formulas  for  a  Fixed  Lime  Standard. 

The  mathematical  part  of  calculating  cement  mixtures  for  a 

fixed  lime  standard  may  be  simplified  by  the  following  formulas, 

which  have  been  used  by  the  writer  in  his  work  and  found  useful. 

The  first  formula  is  for  use  when  the  cement-rock  is  weighed 

and  the  proper  proportion  of  this  weight  of  limestone  is  added. 

/.     To  find  the  percentage  of  a  given  limestone  to  be  added  to 
a  given  cement-rock  or  clay  to  make  a  given  mixture 
Let— 

X  =  Percentage  of  limestone  necessary. 
L,  —  Percentage  of  CaCO3  in  limestone. 
R  —  Percentage  of  CaCO3  in  the  rock  or  clay. 
M  =  Percentage  of  CaCO3  desired  in  the  mixture. 
Then— 


. 

L,  —  M 

Example  —  What  percentage  of  limestone  analyzing  95  per 
cent.  Ca.CO3  must  be  added  to  a  cement-rock  analyzing  70  per 
cent.  CaCO3  to  give  a  mix  analyzing  75  per  cent.  CaCO3? 

Percentage  of  limestone  =  —  —  —  X  100  —  —       =25. 

Hence  to  every  100  Ibs.  of  cement-rock  25  Ibs.  of  limestone 
must  be  added. 

The  next  formula  is  practically  the  same  as  the  last  only  it  is 
intended  for  use  when  the  limestone  or  marl  is  weighed  and  the 
proper  proportion  of  this  weight  of  clay  or  shale  is  added. 

2.  To  find  the  percentage  of  a  given  clay  or  shale  (or  cement- 
rock)  to  be  added  to  a  given  marl  or  limestone  to  make  a  given 
mixture 
Let— 

X  —  Percentage  of  clay  or   shale  necessary. 
C  —  Percentage  of  CaO  in  clay  or  shale. 
L  —    Percentage  of  CaO  in  marl  or  limestone. 
M  =  Percentage  of  CaO  desired  in  the  mixture. 


PROPORTIONING    THE    RAW    MATERIALS  8l 

Then— 


Example  —  What  percentage  of  clay  analyzing  2.5  per  cent. 
CaO  must  be  added  to  a  limestone  containing  53  per  cent.  CaO  to 
obtain  a  mixture  analyzing  41.0  per  cent.  CaO? 

Percentage  clay  =  ^—        -  X  100  =  =  31. 

Instead  of  percentages  of  CaO  percentages  CaCO3,  may  be 
used,  but  if  used  in  one  case,  it  must  be  used  in  all. 

It  sometimes  happens  that  it  is  more  convenient  to  divide  the 
mix  into  percentages  of  limestone  and  of  cement-rock  or  clay  than 
to  make  one  constituent  a  certain  percentage  of  the  other.  For 
example,  when  both  the  limestone  and  cement-rock  are  already 
in  storage  and  both  are  weighed  into  the  same  hopper,  it  makes 
fewer  dumps  necessary,  to  fill  the  hopper  full  each  time  and  to  so 
proportion  the  limestone  and  clay  as  to  just  do  this.  The  follow- 
ing formula  will  give  the  percentage  of  both  the  calcareous  and 
argillaceous  constituents  of  the  mixture. 

5.     To  find  the  percentage  of  a  given  cement-rock  and  of  a 
given  limestone  for  a  given  mix. 
Let— 

X  —  Percentage  of  cement-rock,  shale  or  clay. 

Y  =  Percentage  of  limestone  or  marl. 

R  =  Percentage  of  CaCO3  in  cement-rock,  shale  or  clay. 

L,  =  Percentage  of  CaCO3  in  limestone  or  marl. 

M  =  Percentage  of  CaCO3  desired  in  the  mixture. 
Then— 

M  —  R 

Y  =  —  -IT  X  ioo 

Lf  —  M 

X=  ioo  —  Y 

or 


Y  ==  ioo  —  X. 


82    »  PORTLAND 

Example — What  percentage  of  limestone  analyzing  95  per  cent. 
CaCO3  and  of  cement-rock  analyzing  70  per  cent.  CaCO3  are  re- 
quired in  a  mixture  to  analyze  75  per  cent.  CaCO3? 

Percentage    limestone    =  — ~  X  100  —  — =  20. 

95  -  70  25 

Percentage  cement-rock  =  100  —  20  =  80. 
or 

Percentage  cement-rock  —  ~ —•  X  100  =  — =  80. 

95  —  70  25 

Percentage  limestone  =  100  —  80  •—  20. 

To  illustrate  a  case  where  these  formulas  are  applicable,  let  us 
suppose  that  our  hopper  holds  10,000  Ibs.  then  10,000  X  0.20  or 
2,000  Ibs.  of  this  must  be  limestone  and  10,000  X  O-8o  or  8,000 
Ibs,  must  be  cement-rock. 

As  another  example  let  us  suppose  that  at  a  four  kiln  plant 
there  are  say  six  men  wheeling  limestone  and  cement-rock  from 
separate  piles  to  the  crusher,  and  that  each  barrow  holds  a  maxi- 
mum of  500  Ibs.,  while  the  six  in  rotation  per  trip  usually  handle 
2,500  Ibs.  Now,  20  per  cent,  of  2,500  Ibs.  is,  of  course,  500  Ibs., 
and  80  per  cent,  is  2,000,  so  that  there  must  be  500  Ibs.  of  lime- 
stone for  every  2,000  Ibs.  of  cement-rock.  By  putting  two  men 
on  the  limestone  pile  and  setting  their  scale  at  250  Ibs.  and  four 
men  on  cement-rock  with  their  scale  set  at  500  Ibs.,  the  mix  will 
be  kept  in  proper  proportion. 

After  the  mixture  has  been  made  and  checked,  if  it  is  desired  to 
correct  that  which  has  been  already  ground,  the  two  formulas 
first  given,  as  the  case  may  require,  may  be  used.  If  the  mix 
analyzes  too  low  and  limestone  is  needed  the  first  formula  must 
be  used.  If  too  high  and  clay  is  called  for  the  second  formula 
will  give  the  amount. 

Unfortunately  in  many  mills  no  provision  is  made  for  correct- 
ing the  mix  after  it  leaves  the  grinders  and  the  efforts  of  the 
chemist  are  directed  merely  to  making  the  subsequent  mix  all 
right.  The  formula  given  below  is  for  use  here  and  gives  the 
correct  amount  of  limestone  for  the  new  mixture. 


PROPORTIONING    THE    RAW    MATERIALS  83 

4.  To  calculate  the  correct  percentage  of  limestone  to  be  add- 
ed to  a  cement-rock  from  the  result  of  a  former  mixture  of  the 
two. 

Let— 

M  =  Percentage  of  CaCO3  desired  in  mixture. 
F  —  Percentage  of  CaCO3   found  in  mixture. 
A  =  Percentage  of  limestone  already  added. 
L  —  Percentage  of  CaCO3  in  limestone. 
X  =  Corrected  percentage  of  limestone  needed  to  make  the 
mixture  analyze  M  per  cent.  CaCO3. 

Then— 

X  -  A  4-  (M-F)   (IOQ  +  A) 

L-M 

Example  i.  —  The  mixture  analyzes  74.5  and  should  analyze 
75.0  per  cent.  CaCO3.  20  per  cent,  (of  the  weight  of  the  cement- 
rock)  of  limestone  analyzing  95  per  cent.  CaCO3  was  added. 
What  amount  should  be  added? 

x  =  20   ,    (75  —  74-5)  (100  +  20)  =  0.5  X  120  _ 

95  -  75  20 

.   60 
20  H  --  :  =  23  per  cent. 

Example  2.—  The  mixture  analyzes  76.0  per  cent.  CaCO3  and 
should  analyze  75.0  per  cent.  CaCO3,  If  20  per  cent,  of  95  per 
cent,  limestone  has  been  added,  to  what  should  this  be  reduced? 


X--Q   |    (75-76)    (ioo+2o)  =  2Q      -ix  120 

95  ~  75  20 

20  —  6  =  14  per  cent. 

Where  clay  is  added  to  limestone  or  marl  and  where  formula 
2  has  been  used  to  calculate  the  mix  then  formula  4  becomes  as 
follows  : 

5-  To  calculate  the  correct  percentage  of  clay  or  shale  to  be 
added  to  a  limestone  or  marl  from  the  result  of  a  former  mixture 
of  the  two. 


84  PORTLAND  CEMENT 

Let— 

M  =  Percentage  of  CaO  desired  in  mixture. 
F  =  Percentage  of  CaO  found  in  the  mixture. 
B  =  Percentage  of  clay  already  added. 
C  =  Percentage  of  CaO  in  clay. 

X  =  Corrected  percentage  of  clay  needed  to  make  the  mix- 
ture analyze  M  per  cent.  CaO. 
Then— 

(M-F)    (IOQ  + B) 

~F^-  C~ 

When  it  is  customary  to  divide  the  mix  into  percentages  and 
where  formulas  No.  3  have  been  used  to  calculate  the  mix  the 
formula  given  below  will  arrive  at  the  corrected  percentages  of 
cement-rock  and  of  limestone. 

6.     To  calculate  the  correct  percentage  of  limestone  and  of  ce- 
ment-rock in  a  mixture  from  the  result  of  a  former  mixture. 
Let— 

M  =  Percentage  of  CaCO3  desired  in  mixture. 
F  =  Percentage  of  CaCO3  found  in  mixture. 
A  =  Percentage  of  limestone  already  in  mixture. 
L  =  Percentage  of  CaCO3  in  the  limestone. 
X  =  Corrected  percentage  of  limestone  to  make  the  mix- 
ture analyze  M  per  cent.  CaCO3. 
Then— 

(M-F)   (IPO -A) 

L-F 

Y  —  100  —  X. 

Example — The  mixture  analyzes  74.5  and  should  analyze  75.0. 
The  mixture  is  composed  of  20  per  cent,  limestone  analyzing  95 
per  cent.  CaCO3,  80  per  cent,  cement-rock.  What  are  the  cor- 
rect proportions? 

i    (75—74-5)  (100—20)  .  0.5X80 

X=^2o+ ^-^ — '^        ^=20+  —         -  —21.95— about  22 

95—74.5  20.5 

Y  —   100  22   =   78. 

In  formula  No.  6  it  is  assumed  that  the  percentage  of  CaCO8 


PROPORTIONING    THE    RAW    MATERIALS  85 

in  the  limestone  is  correct  and  that  the  error  in  the  mix  causing 
it  to  be  74.5  instead  of  75.0  CaCO3  is  due  to  the  failure  to  prop- 
erly sample  the  cement- rock.  If  clay  is  added  to  the  rock  or  lime- 
stone for  the  mixture  it  is  better  to  assume  the  clay  to  be  correct, 
in  which  case  we  have  the  following: 

7.  To  calculate  the  percentage  of  clay  or  shale  and  of  lime- 
stone or  marl  in  a  mixture  from  the  result  of  a  former  mixture. 

Let— 

M  —  Percentage  of  CaO  desired  in  mixture. 

F  =  Percentage  of  CaO  found  in  mixture. 

B  =  Percentage  of  clay  or  shale  already  in  mixture. 

C  =  Percentage  of  CaO  in  clay  or  shale. 

Z  .=  Correct  percentage  of  clay  or  shale  in  the  mixture  to 

make  it  analyze  M  per  cent.  CaO. 
X  =  Corrected  percentage  of  limestone  or  marl. 

Then— 

(F— M)  (IOQ -B) 

F-C 

X  —  100  —  Z. 

Example. — The  mixture  analyzes  '40.5  and  should  analyze  41.0 
per  cent.  CaO.  The  mixture  is  composed  of  24  per  cent,  clay 
and  76  per  cent,  limestone.  Clay  analyzes  3  per  cent.  CaO. 
What  are  the  correct  proportions? 

(40.5  —  41.0)  (IOQ  —  24)  _  —0-5X76 _ 

LI  —  ^4    i  ~  —  -^4    i 

40-5  —  3  37-5 

24  —  i.o  =  23  per  cent. 

X  =  100  —  23  =  77. 

A  slide  rule  will  greatly  facilitate  rapid  calculation  of  cement 
mixture  and  changes  to  be  made  in  the  same. 

A  lo-inch  one  can  be  bought  for  as  little  as  $1.25  and  will  be 
found  to  come  in  very  handy  for  other  laboratory  calculations 
where  accuracy  is  not  required  to  more  than  three  figures,  such 
as  figuring  out  the  percentage  of  sulphuric  anhydride  and  mag- 
nesia in  an  analysis. 


86 


PORTLAND  CEMENT 


A  simple  table  of  the  quotients  of —   or  — ^  ,  which 

L  —  M        M  —  L 

ever  is  used,  will  greatly  aid  calculations.     Formula  I  will  then 


become  X  =  (M  —  R)  Q  when  Q  == 


100 


— M 


,  and  formula   2   will 


be  X  =  (L  —  M)  R  where  R  = 


100 


M 


Below  is  given  such  a 


table  for  a  mix  desired  to  contain  75  per  cent.  CaCO3,  and  for 
limestone  ranging  from  92  to  98  per  cent  CaCO3. 

VALUES  OF  Q,  MIXTURES  —  75.0  PER  CENT.  CaCO. 


Per  cent.  CaCO3  in  limestone 

Q, 

Per  cent.  CaCO3  in  limestone 

Q 

92.0 

5-9 

95-5 

4-9 

92.5 

5-7 

96.0 

4.8 

93-0 

5-6 

96.5 

4-7 

93-5 

5-4 

97.0 

4-5 

94.0 

5-3 

97-5 

4.4 

94-5 

5-i 

98.0 

4-3 

95-o 

5-0 

98.5 

4.2 

Using  this  table  in  the  example  given  under  I. 

Percentage  of  limestone  —  (75-70)   X  5  =  25. 

When  a  three  component  mix  is  employed  as  for  example  where 
sandstone  is  added  to  supply  a  deficiency  of  silica  in  the  shale, 
the  following  method  of  calculating  the  proper  proportion  of 
each  element  so  as  to  give  definite  ratios  between  the  silica 
and  the  alumina,  on  the  one  hand,  and  the  silica,  iron  oxide  and 
alumina,  on  the  other,  will  be  found  convenient  and  exact. 

Let  the  following  represent  the  analysis  of  the  three  components 
respectively. 

Limestone  Shale  Sandstone 

Silica    Sx  S2  S3 

Oxide  iron  and  alumina Ox  O2  O3 

Lime  (or  carbonate) Lx  L2  L3 

Let  r  and  R  represent  the  ratios  desired  as  follows : 
Silica 


r  = 


R  = 


Iron  oxide  -f-  alumina 

Lime 
Silica  -f-  iron  oxide  +  alumina  ' 


PROPORTIONING    THE    RAW    MATERIALS  87 

Now  solve  the  following: 

a  =  S±  -  -  rOi. 
b  =  rO2  —  S2. 
c  =  r03  —  S.. 

d    =    Lx    -   -    (Si    +    OJR. 

^  =  (S2  +  Oe)R  —  L2. 
/   =  (S8  +  03)R  —  L8. 

The  proportions  of  the  three  components  will  then  be  as  fol- 
lows: 

Limestone   :  sandstone   :  shale. 
ec  —  bf  :    ea  —  bd    :  cd  —  fa 

Or  if 

Limestone  =  100. 


ea  —  bd 

Sandstone  =  -      —  r?  X  100. 
ec  —  bf 

Example.  —  Find  the  proportions  in  which  to  mix  the  three 
materials  whose  analyses  are  given  below  so  that  the  ratios  be- 
tween the  silica  and  the  oxides  will  be  2  and  the  ratio  be- 
tween the  carbonate  of  lime  and  the  silica  and  oxides  will  be  4. 

ANALYSES. 

Limestone  Shale  Sandstone 

Silica    ..............................     2.4  50.2            75-6 

Iron   oxide  and  alumina    ...........     0.8  324            JS-4 

Carbonate  of  lime    .................  95-Q  4-3             2.2 

Carbonate  of   magnesia    ............     1.8  2.1              2.4 

Solution.  — 

a  —  2.4  —1.6  =  0.8.  b  =  64.8  —  50.2  =  14.6. 

c  =  30.8  -  -  75.6  =  -  -  44-8. 
d  =  95.0  —(2.4  +  0.8)   X  4  =  82.2. 
e  =  (50.2  +  32.4)  X  4  —  4-3  =  326.1. 

/  =    (75.6  —  154)    X  4  —  2.2   =   362.8. 


88  PORTLAND  CEMENT 

Limestone  =   100  Ibs. 

(-44.8  X  82.2)  — (362.8  X  0.8) 
(326.1  X  -44-8)  -  (14.6  X  362.8)     X 
=  -3,972.80  X  zoo  =  bg 

—19,906.16 

(326.1  X  0.8)  —  (14.6  X  82.2) 
SandStODe  ^  =  (326  IX -44-8) -(14.6X362.8)  X  I0° 

—939.24  X  IPO 
— 19,906.16 

The  above  calculations  can  be  made  in  a  few  minutes  with  a 
slide  rule.  Mr.  L.  T.  Bachman,  chemist  of  the  Santa  Cruz 
Portland  Cement  Co.,  has  devised  for  his  own  use  an  ingenious 
system  of  tables  and  formulas  which  reduce  to  a  minimum  the 
calculations  required  for  a  three  component  mix.  These  are 
in  constant  use  at  this  plant  where  a  shale  high  in  silica  is  em- 
ployed in  connection  with  one  high  in  alumina. 

Controlling  the  Mixture  in  the  Wet  Process. 

For  controlling  the  mixture  in  mills  using  marl  and  clay  and 
consequently  the  wet  process,  many  methods  are  in  vogue.  At 
some  of  the  plants  the  slurry  is  merely  dried  and  the  carbonate  of 
lime  determined  in  the  usual  manner  as  outlined  in  Chapter  XI, 
either  by  titration  with  standard  N/2  acid  and  alkali  or  by  meas- 
uring the  volume  of  carbon  dioxide  liberated  in  the  Scheibler's 
calcimeter.  Another  plan  and  one  which  is  in  use  in  the 
laboratory  of  the  Omega  Portland  Cement  Co.,  Jonesville,  Mich., 
is  to  determine  the  lime  by  titration  with  standard  N/2  acid 
and  alkali,  and  also  "the  silicates."  The  determination  of  the  latter 
is  also  given  in  the  chapter  on  "The  analysis  of  the  mix."  The 
ratio  between  the  silicates  and  the  lime  is  then  kept  constant.  In 
a  sample  of  correctly  proportioned  slurry  upon  which  this  deter- 
mination was  made,  the  ratio  was  3.8.  This  ratio  undoubtedly 
will  vary  at  different  mills,  and  also  with  any  variations  in  the 
manner  of  carrying  out  the  determination  of  the  silicates,  so  that 
this  ratio  must  be  fixed  by  experience.  At  a  new  mill  it  could 
be  determined  to  some  extent  before  beginning  operations  by 


PROPORTIONING    THE    RAW    MATERIALS  89 

making  up  a  set  of  "standard  samples"  (using  the  formula 
given  on  page  71  to  determine  the  proper  proportions)  from 
various  lots  of  marl  and  clay.  The  marl  for  these  samples 
should  be  so  selected  as  to  cover  the  range  expected  to  be 
met  with  in  practice.  This  applies  to  the  clay  also.  The  ratios 
between  the  lime  and  the  silicates  should  then  be  determined  and 
if  found  fairly  constant  it  can  be  adopted.  If  possible  these 
samples  should  be  checked  by  burning  in  a  small  kiln  and 
examining  the  properties  of  the  resulting  cement.  It  may  be 
found  necessary  after  starting  up  the  mill  to  raise  or  lower  this 
ratio. 

At  the  two  mills  of  the  Sandusky  Portland  Cement  Co.,  the 
mix  is  controlled  by  the  ratio  between  the  percentage  of  lime, 
determined  by  acid  and  alkali,  and  the  percentage  of  "insoluble," 
as  determined  by  boiling  one  gram  for  5  minutes  with  10  per 
cent,  hydrochloric  acid,  filtering,  washing,  igniting,  and  weighing. 
This  ratio  is  also  different  for  different  works.  At  the  Sandusky 
plant  of  the  above  company  the  ratio  is  about  3.9  and  at  the 
Syracuse,  Ind.,  mill  4.2,  the  difference  being  due  to  a  greater 
amount  of  carbonate  of  magnesia  and  a  more  silicious  clay  at  the 
latter  mill.  This  ratio  must  be  fixed  like  the  lime-silicate  ratio 
by  comparison  with  samples  carefully  analyzed. 

The  author  has  used  the  following  method  of  control  as  doing 
away  with  the  uncertainties  due  to  water  and  organic  matter  in 
clay-limestone  mixtures  and  in  slurry:  Measure  into  a  large 
weighed  platinum  crucible  such  a  quantity  of  wet  slurry  as  will 
give  about  0.8  gram  of  dried  slurry  (or  that  amount,  0.8  gram, 
direct  of  dried  slurry).  Dry  rapidly,  avoiding  any  loss  by 
spattering  if  necessary,  ignite  cautiously  at  first,  then  strongly 
for  5  minutes  over  a  Bunsen  burner,  and  then  for  10-15  minutes 
over  a  blast.  The  result  will  be  a  clinker  of  practically  the  same 
composition  as  that  obtained  in  the  kiln  except  that  it  lacks  the 
fuel  ash.  The  crucible  and  contents  are  then  weighed  and  the 
weight  of  the  clinker  calculated.  The  lime  is  then  determined 
in  this  clinker  by  the  rapid  permanganate  method  given  in 
Chapter  X.  This  gives  an  excellent  check  on  the  slurry,  if  the 


9O  PORTLAND  CEMENT 

magnesia  is  anywhere  near  constant,  as  it  is  only  necessary  to 
keep  the  lime  in  this  clinker  around  a  constant  figure.  The 
sample  of  wet  slurry  may  be  rapidly  dried,  in  the  crucible,  in  the 
following  manner:  Incline  the  crucible  on  a  tripod  over  a 
burner  turned  low,  in  such  a  way  that  the  flame  plays  under  the 
upper  part  of  the  crucible.  This  will  cause  a  rapid  evaporation 
of  the  water.  When  the  mass  looks  dry  the  burner  can  be  moved 
back  gradually  until  it  plays  upon  the  mass  directly  and  allowed 
to  remain  here  5  minutes  when  the  crucible  is  ready  for  the  blast. 
The  lime  will  be  somewhat  higher  in  this  artificially  prepared 
clinker,  than  in  that  from  the  kilns,  owing  to  the  contamination  of 
the  latter  by  the  fuel  ash,  and  still  higher  in  lime  than  the  finished 
cement  in  which  it  is  lowered  by  the  addition  of  gypsum  and  the 
absorption  of  water  from  the  air.  What  the  lime  should  be  in 
the  clinker  can  easily  be  determined  by  applying  the  method  to 
samples  of  the  mixture  which  have  been  subjected  to  complete 
analysis  and  found  to  be  of  correct  composition. 

In  making  the  mixture  with  wet  materials  such  as  clay  and 
marl  the  water  and  organic  matter  are  disturbing  elements.  In 
order  to  make  the  mixture  with  these  materials  it  is  necessary  to 
determine  the  percentage  of  water  they  contain,  and  from  this  to 
calculate  the  weight,  of  wet  marl  or  clay  equal  to  a  given  weight 
of  dry  material.  For  instance  suppose  the  marl  to  contain  60 
per  cent,  water  and  the  clay  15  per  cent.  Then  100  Ibs.  of  wet 
marl  would  only  contain  100-60  or  40  Ibs.  dry  marl,  and  from  the 
proportion 

(40:100:  :ioo:X) 
We  find  250  Ibs.  of  wet  marl  equivalent  to  100  of  dry  marl. 

If  loo  Ibs.  of  dry  marl  require  31  Ibs.  of  dry  clay,  it  would  re- 
quire 36.4  Ibs.  of  wet  clay  by  a  similar  calculation.  So  that  our 
proportions  would  be  250  of  wet  marl  to  36.4  of  moist  clay. 

This  will  apply  to  the  use  of  any  of  the  formulas  given  in  this 
chapter,  when  used  for  calculations  involving  wet  materials.  The 
results  will  be  in  pounds  of  dry  material  and  must  then  be  calcu- 
lated to  wet  marl,  clay  or  slurry.  In  using  the  ratio  between 
either  the  lime  and  the  silicates  or  the  lime  insoluble,  the  lime 


PROPORTIONING    THE    RAW    MATERIALS  9! 

and  the  silicates  must  be  found  in  the  marl,  and  the  silicates  (and 
lime  if  any)  in  the  clay,  if  the  first  method  is  used ;  and  the  lime 
and  the  insoluble  in  the  marl,  and  the  insoluble  in  the  lime,  if  any, 
in  the  clay,  if  the  second  method  is  to  be  used,  in  order  to  pro- 
portion the  two.  The  following  formula  will  give  the  proper 
proportions  of  clay  and  marl  to  make  a  slurry  of  a  given  ratio. 
Let- 

L  =  Lime  in  the  marl. 

/    —    Lime  in  clay. 

S  =  Silicates    (or  insoluble)   in  marl. 

s    =    Silicates  (or  insoluble)  in  clay. 

R  =    Ratio  =  57^ — 

Silicate  (or  insoluble) 

Then- 
Mar^        R  X  s  —  I 
Clay      ~~  L  — RXS  ' 

This  formula  may,  of  course,  be  used  to  correct  a  slurry  found 
to  be  too  high  or  low  in  lime.  In  this  event,  if  the  clay  is  called 
for,  the  lime  and  silicates  in  the  slurry  should  be  represented  by 
L  and  S,  but  if  marl  is  needed,  by  /  and  s. 

Calculating  the  Probable  Analysis  of  the  Cement  Clinker. 

The  problem  of  determining  the  probable  composition  of  a 
cement  from  its  raw  materials  is  often  put  up  to  the  chemist. 
The  solution  is  by  no  means  easy.  The  usual  rule  is  to  add  to- 
gether the  percentages  of  silica,  oxide  of  iron  and  alumina,  lime 
and  magnesia  and  to  divide  this  sum  into  the  percentage 
of  each  compound,  multiplied  by  100,  for  the  percentage 
of  that  compound  which  will  be  present  in  the  clinker.  If 
this  rule  is  followed,  the  results  obtained  for  silica  and  for  iron 
oxide  and  alumina  will  be  too  low  and  the  lime  much  too  high 
unless  oil  or  natural  gas  is  used  for  fuel  in  burning.  This  is  be- 
cause the  ash  of  the  fuel  enters  into  the  composition  of  the 
clinker  and  also  because  the  clinker  contains  other  constituents 
present  in  the  raw  materials  which  are  not  volatilized  in  burning: 


92  PORTLAND  CEMENT 

viz.,  soda,  potash,  some  of  the  sulphur  which  oxidizes  to  sulphur 
trioxide,  carbon  dioxide,  water,  etc. 

To  accurately  calculate  the  composition  of  the  clinker  from 
the  analysis  of  the  raw  material  is,  therefore,  impossible,  and  the 
best  we  can  do  is  to  assume  certain  corrections.  First  of  these 
is  for  the  coal  ash  entering  into  the  clinker.  My  own  experi- 
ments show  that  in  the  rotary  kiln  about  one-half  the  ash  enters 
the  clinker.  The  West  Virginia  gas  slack  coal  contains  about 
10  per  cent,  ash  on  the  average.  This  ash  is  composed  of  about 
40  per  cent,  silica  and  about  20  per  cent,  each  of  iron  oxide  and 
alumina.  If,  therefore,  90  Ibs.  of  coal  are  required  to  burn  a 
barrel  of  cement  about  15  Ibs.  (equivalent  to  1.5  Ibs.  of  ash)  are 
required  per  100  Ibs.  of  raw  material  burned.  Assuming  half 
the  ash  to  enter  the  raw  material,  the  silica  in  the  latter  is  in- 
creased by  y2  X  1.5  X  040  =  0.30  per  cent.,  and  the  iron  and 
alumina  each  by  y>  X  i-5  X  0.20  =  0.15  per  cent. 

Analyses  of  Lehigh  Valley  clinker  when  fresh  from  the  kilns 
show  it  to  contain  about  2  per  cent,  of  potash,  soda,  sulphur  com- 
pounds, carbon  dioxide  and  water  combined.  Clinker  from  other 
localities  will  probably  not  vary  very  widely  from  this. 

Assuming  the  above  corrections,  my  rule  for  calculating  clinker 
from  the  mix  analysis  is  as  follows : 

Add  together  the  percentages  of  silica,  oxide  of  iron,  alumina, 
lime  and  magnesia.  To  the  sum  add  2.75.  Call  the  result  the 
"Clinker  total." 

To  find  the  percentage  of  silica,  add  0.30  to  the  percentage  of 
silica  in  the  raw  material,  multiply  the  sum  by  100  and  divide 
by  the  "Clinker  total"  as  found  above.  The  result  will  be  the 
percentage  of  silica  in  the  clinker. 

To  find  percentage  of  iron  oxide,  add  0.15  to  percentage  of 
alumina  in  the -mix,  multiply  by  100  and  divide  by  "Clinker 
total,"  etc. 

To  find  percentage  of  lime  or  magnesia,  divide  percentages  of 
these  by  "Clinker  total,"  etc. 


PROPORTIONING    THE    RAW    MATERIALS  93 

ANALYSIS  OF  RAW  MATERIAL. 

Silica 13-44 

Oxide  of  iron  and  alumina  . .  •  • 6.54 

Lime 41.84 

Magnesia 1.93 

63.75 

Correction  for  ash,  etc ; 2.75 

Clinker  total 66.50 

Percentage  of  silica: 

ioo  X  13'44  +  °-3°   =20.66. 

66.50 

Percentage  of  iron  oxide  and  alumina: 

6. 54.  4-  o.  ^o 

ioo  X      *\7 — —  =  10.29. 
66.50 


Percentage  of  lime: 

ioo  X  41.84 
66.50 

Percentage  of  magnesia: 
ioo  X  i.93 


=  62.92. 


66.50 

Probable  composition  of  clinker: 

Silica 20.66 

Iron  oxide  and  alumina 10.29 

Lime 62.92 

Magnesia 2.90 

When  coal  containing  higher  percentages  of  ash  or  ash  of  a 
different  chemical  composition  than  that  given  above  is  em- 
ployed for  burning,  the  chemist  using  the  above  as  a  guide  can 
readily  calculate  the  corrections  to  be  applied. 


Chapter  V. 


QUARRYING,  EXCAVATING,   DRYING  AND  MIXING 
THE  RAW  MATERIALS. 

Quarrying  Stone. 

Limestone,  cement-rock  and  shale  are  usually  quarried,  while 
clay  is  dug  from  pits  and  marl  is  dredged,  often  from  under 
water.  Deposits  of  cement-rock  and  limestone  are  usually  over- 
laid by  a  few  feet  of  soil  and  clay  which  must  be  removed  by 
scrapers  or  shoveling.  When  clay  is  used  to  make  the  mix,  this 
surface  deposit  is  conveyed  to  the  mill,  otherwise  it  is  carted 
away  to  a  dump.  In  one  or  two  plants,  notably  those  located 
near  Wellston,  O.,  it  is  necessary  to  mine  the  limestone,  owing 
to  the  dip  of  the  material,  which  carries  down  under  other  rock. 
This  method  rarely  pays,  however,  as  in  order  to  meet  competi- 
tion, it  is  necessary  to  deliver  the  rock  to  the  mill  at  lower  cost 
than  will  permit  of  mining.  Shale  is  also  occasionally  mined 
and  the  Atlas  Portland  Cement  Co.,  at  Hannibal,  Mo.  mill,  mine 
their  shale.  As  much  less  shale  is  employed,  mining  shale  is  not 
so  expensive  as  mining  the  limestone. 

Some  deposits  of  rock  and  limestone  are  so  situated  that  they 
can  be  opened  on  a  hillside,  at  others,  it  has  been  necessary  to  go 
straight  down.  When  a  deposit  is  opened  on  the  side  of  a  hill 
the  cars  can  usually  be  run  to  the  latter  at  a  slight  grade.  At 
the  plant  of  the  Bath  Portland  Cement  Co.,  Bath,  Pa.,  where  this 
is  done,  the  cars  are  run  down  to  the  mill  by  gravity,  dumped, 
then  elevated  to  a  trestle  and  run  back  by  gravity  also. 

The  stone  is  usually  blasted  down  in  benches,  sometimes  along 
the  whole  face  of  the  quarry  at  once,  at  others,  only  a  small  part 
of  a  bench  at  a  time.  The  drill  holes  for  the  blasting  are  usually 
made  with  power  drills,  run  by  steam  or  compressed  air,  and  are 
carried  to  a  depth  of  16  to  20  feet.  Of  late  years  a  great  deal 
of  blasting  is  being  done  by  means  of  well  digging  or  churn 


QUARRYING,    EXCAVATING,    ETC.,    OF    RAW    MATERIAL  95 

drills  and  instead  of  blasting  the  rock  down  in  benches,  throw- 
ing down  the  whole  face,  usually  40,000  to  75,000  tons  of  rock 
at  once,  the  object  being  to  save  clearing  off  the  benches  and 
the  trouble  often  experienced  of  setting  up  small  drills  on 
irregular  and  sloping  benches.  In  using  these  drills,  6  inch 
holes,  extending  downward  from  the  top  of  the  rock  to  four  or 
five  feet  below  the  quarry  floor  and  16  to  20  feet  back  from  the 
quarry  face  are  sunk.  These  are  then  loaded  with  dynamite  and 
the  whole  row  of  holes  are  fired  at  once.  At  a  number  of 
quarries  in  the  Lehigh  district  where  this  system  has  been  tried, 
it  has  not  only  been  found  cheaper  but  also  much  more  satis- 
factory for  furnishing  the  mill  with  a  constant  supply  of  stone 
of  regular  composition.  The  system,  however,  is  not  very  well 
adapted  to  opening  a  new  quarry. 

In  blasting,  an  effort  is  made  to  shatter  the  rock  as  much  as 
possible,  in  order  to  save  subsequent  sledging  and  blasting  to 
break  up  the  big  pieces.  In  spite  of  this  attempt  it  is  necessary 
at  f3ractically  all  quarries,  except  that  of  the  Edison  Portland 
Cement  Co.,  to  break  up  many  big  pieces  of  rock  either  with 
dynamite  or  hand  sledges.  The  rule  at  the  present  time  among 
cement  mill  engineers,  however,  is  the  installation  of  very  large 
gyratory  crushers,  which  practically  eliminate  hand  sledging  and 
only  require  that  the  very  big  rocks  be  broken  up  by  dynamite, 
but  most  of  the  older  mills  only  have  the  small  crushers,  for 
which  much  of  the  rock  must  be  broken  by  hand.  It  seems 
curious,  in  this  connection,  that  no  one  has  tried  the  use  of  air 
or  electric  hammers  to  do  the  work  of  hand  sledges.  They 
would  be  much  cheaper  than  hand  sledging  and  would  un- 
doubtedly break  up  the  rock. 

Where  many  large  rocks  have  to  be  broken  up  by  dynamite,  a 
small  hand  air  drill  will  be  found  more  convenient  for  this 
purpose  than  anything  else.  The  air  drills  can  be  attached  to  a 
long  piece  of  strong  flexible  hose  coupled  to  the  air  line  and  used 
to  drill  rocks  in  any  part  of  the  quarry.  In  a  few  minutes  time 
a  hole  a  foot  deep  can  be  drilled  in  cement-rock,  and  this  can  then 
be  filled  with  dynamite  and  the  rock  shattered. 


96  PORTLAND  CEMENT 

After  breaking  up  to  a  size  suitable  for  crushing  and  loading, 
the  rock  is  ready  for  the  mill. 

In  some  quarries  the  stone  is  loaded  on  carts  and  carried  to 
a  point  out  of  danger  from  the  blasting  and  dumped  into  side  or 
end  dump  cars  which  are  hauled  or  dropped  by  gravity  to  the 
mill.  At  other  mills,  temporary  tracks  are  laid  from  a  turn-table 
or  switch  at  the  end  of  the  tracks  leading  to  the  mill  to  the  rock 
piles,  and  the  cars  are  loaded  direct  from  these,  and  then  hauled 
to  the  mill  as  before.  When  the  quarrying  has  been  carried 
straight  down,  the  rock  is  loaded  on  skips,  which  are  carried  to 
the  mill  by  an  aerial  cable  and  hoist.  The  cars  are  loaded  by 
hand  at  many  cement  mills  and  a  great  deal  of  sledging  is 
necessary  in  order  to  reduce  the  rock  to  a  size  suitable  for  handling 
and  crushing.  At  a  few  of  the  larger  mills  steam  shovels  are 
used,  but  they  interfere  to  some  extent  with  blasting  and  the 
crushers  at  most  of  The  mills  are  too  small  to  take  rock,  as  it 
comes  from  the  pile,  without  being  broken  up.  Then,  too  with 
cement-rock,  unless  the  deposit  is  very  regular,  the  steam  shovels 
localize  the  quarrying  so  that  the  cement  is  not  so  uniform  as  if 
a  large  face  were  worked.  Nevertheless,  they  are  being  intro- 
duced gradually,  in  connection  with  larger  crushers  and  the 
chemist  usually  works  out  a  way  around  the  difficulty  of  an 
irregular  composition.  When  the  material  is  of  a  regular  com- 
position such  as  is  often  the  case  with  limestone,  shale  or  clay, 
steam  shovels  can  be  used  to  advantage  and  on  the  latter  two 
classes  of  material  are  pretty  generally  used.  The  steam  shovels 
employed  are  usually  of  about  ij^  to  2  tons  capacity.  If  too 
small  they  will  seldom  show  any  economy  over  hand  loading, 
but  when  large  enough  will  load  cheaper,  particularly  when  good 
labor  is  higher  than  $1.25  per  day.  As  clay  is  soft  the  steam 
shovel  can  both  dig  out  the  clay  and  load  it  on  the  cars.  Usually 
it  is  necessary  to  carry  the  clay  some  distance,  for  the  mill  is 
always  located  as  near  the  marl  or  limestone  as  possible,  as  four 
or  five  times  as  much  of  these  are  used  as  of  clay  or  shale.  Clay 
can  generally  be  dug  without  blasting  but  shale  usually  has  to  be 
broken  up  by  means  of  drilling  and  dynamite  or  black  powder. 


Fig.  4.— 95-ton  Bucyrus  steam  shovel — Edison  Portland  Cement  Co. 


Fig.  7. — i-yard  Bucyrus  dredge— Coldwater  Portland  Cement  Co. 


QUARRYING,    EXCAVATING,    ETC.,    OF    RAW    MATERIAL 


97 


The  hauling  of  the  stone  to  the  mill  is  generally  done  mechanical- 
ly although  at  a  few  works  horses  or  mules  are  employed  while 
at  a  few  others  a  gravity  system  may  be  operated.  The  methods 
employed  for  mechanically  drawing  cars  up  to  the  mill  consist 
of  a  cable  and  either  a  steam  or  electrically  driven  drum 
hoist.  When  the  quarry  is  some  distance  away  from  the 
mill,  a  steam  or  electric  locomotive  may  be  employed  to  best 
advantage.  The  cars  generally  require  to  be  dumped  by  hand 
but  at  the  best  equipped  mills  the  dumping  is  done  automatically, 


Fig.  5. — Automatic  system  of  dumping  cars.     (Allentown  Portland  Cement  Co.) 

the  cars  employed  being  end  dump  cars.     This  usually  saves  at 
least  two  men  and  sometimes  more. 

Fig.  5  shows  the  system  employed  at  the  plant  of  the  Allentown 
Portland  Cement  Co.  for  automatically  dumping  the  cars  into 
the  large  crusher.  Here  the  cars,  c  are  end  dump  cars  of  about 
3^4  tons  capacity.  The  door  is  held  shut  by  means  of  a  bar,  a, 
working  on  a  pivot  at  about  the  middle  of  the  door  face.  This 
bar  extends  about  six  inches  beyond  the  side  of  the  car  and  drops 
into  a  catch,  b,  bolted  to  the  side  of  the  car,  thus  securely  fasten- 
ing the  door.  When  the  car  coming  up  the  incline  reaches  the 
proper  dumping  point,  above  the  crusher,  the  part  of  the  bar 
7 


98  PORTLAND  CEMENT 

projecting  beyond  the  car  slides  over  a  rack,  d,  at  the  side  of 
the  track,  and  as  the  car  moves  farther  up  the  incline,  the  bar  is 
lifted  out  of  the  catch  by  the  pitch  of  this  rack,  allowing  the  door 
to  be  forced  open  by  the  weight  of  rock  against  it. 

Fig.  6  shows  the  arrangement  of  the  track  and  crusher  usually 
employed  where  the  cars  are  dumped  by  hand.  The  gabled 
bottomed  cars  shown  in  this  illustration  are  convenient  as  they 
are  easily  dumped.  The  rock  falls  on  both  sides  of  the  crusher 


Fig.  6.— Common  arrangement  of  track  and  crusher  for  hand  damping  of  cars. 

and  they  stand  low  on  the  track,  allowing  easy  hand  loading,  as 
the  men  do  not  have  to  lift  the  rock  so  high  in  order  to  get  it 
into  the  car.  They  are  not  very  well  suited  to  steam  shovel  load- 
ing, however,  as  the  big  rocks  are  likely  to  break  the  peak  of  the 
gable.  v 

Excavating  Marl. 

Marl  as  has  been  said  carries  considerable  water  and  the  de- 
posits usually  lie  in  depressions  and  underneath  the  surface  of  a 
shallow  lake  or  marsh.  In  some  instances,  the  marl  deposit  is 
overlaid  by  a  foot  or  more  peat  which  must  be  dredged  off.  In 
excavating  the  marl  several  plans  are  followed,  one  of  the  most 
common  is  that  of  a  steam  dredge  mounted  on  a  barge  which 
scrapes  up  the  marl  from  the  bottom  of  the  lake  and  loads  it  on 


QUARRYING,    EXCAVATING,    ETC.,    OF    RAW    MATERIAL 


99 


barges.  These  barges  are  then  towed  to  the  wharf  and  unloaded 
by  machinery  on  belt  conveyors  which  carry  the  marl  to  the  mill. 
This  can,  of  course,  be  done  only  where  the  marl  lies  under  water. 
When  the  beds  have  been  drained,  it  is  usual  for  the  steam  dredge 
or  shovel  to  float  on  its  barge,  in  the  channel  which  it  cuts  out  of 
the  marl,  and  to  load  the  marl  on  to  cars,  running  on  temporary 
tracks,  on  a  bank  by  the  barge.  The  channel  fills  with  ground 
water  and  the  bank  is  thrown  up  by  the  dredge  either  from  the 
stripping  on  top  of,  or  the  material  underneath  the  marl.  Instead 
of  using  barges  and  cars  to  convey  the  marl  to  the  mill  some  of 
the  Michigan  mills  drop  their  marl  from  the  scoop  of  the  dredge 
into  the  hooper  of  a  pug  mill  on  a  boat  or  car.  Here  the  marl  is 


Q-Q-, 


Fig.  8.— Pug  mill  (Bonnot  Co.). 

mixed  with  water  to  form  a  thin  mud,  which  is  pumped  to  the 
mill  through  a  pipe  line,  carried  over  the  marsh  or  marl  bed  on  a 
wooden  trestle.  The  steam  dredges  are  of  the  same  type  as  those 
used  for  excavating  cuts  by  railroads  and  for  deepening  the  chan- 
nels of  rivers  and  harbors.  They  consist  of  a  scoop  or  dipper 
having  a  hinged  bottom  and  fixed  to  a  long  arm.  This  arm  can 
be  swung  to  either  side,  raised,  lowered  or  pushed  forward,  by  a 
system  of  chains,  racks  and  pinions.  Some  of  the  dredges  are  of 
the  orange  peel  bucket  type.  These  have  a  bucket  hanging  from  a 
revolving  arm  by  cables  or  chains,  which  opens  and  shuts  and  is 
filled  by  lowering  open  to  the  bottom  of  the  lake  and  then  closing. 
Fig.  7  shows  a  steam  dredge  such  as  is  used  in  excavating  marl. 
The  pug  mills,  Fig.  8,  used  in  cement  works  are  similar  to 


100 


PORTLAND 


those  used  in  the  better  equipped  brick  yards,  and  consist  of  a 
long  steel  cylinder,  in  which  revolve  two  shafts  provided  with 
steel  blades.  The  mixture  of  marl  and  clay  enters  at  one  end  and 
is  forced  out  at  the  other.  During  its  passage  it  is  churned  up  by 
the  blades  and  thoroughly  mixed.  When  the  marl  is  pumped  from 
the  lake  to  the  mill,  it  is  usual  to  locate  a  separator  on  the  barge 


Fig.  9. — Harris  system  of  pumping  marl 
by  compressed  air. 


Fig.  10. — Ball  valve  slurry 
or  marl  pump. 


to  take  out  the  sticks,  roots,  etc.  This  generally  consists  of  a  per- 
forated screen  through  which  the  marl  is  forced.  The  separator 
also  serves  as  a  pug  mill  in  reducing  the  marl  to  a  uniform  paste. 
The  best  system  of  pumping  marl  is  with  compressed  air.  In 
this  system  of  pumping,  there  are  two  cylinders  located  side  by 
side,  both  of  which  are  connected  with  the  air  compressor.  One 
of  these  cylinders  is  being  drawn  full  of  slurry  by  the  compressor 


QUARRYING,    EXCAVATING,    ETC.,    OF    RAW    MATERIAL          IOI 

while  the  other  is  being  emptied.  When  used  for  pumping  marl 
to  the  mill  the  cylinders  and  air  compressor  are:  located^on  the 
barge.  Fig.  9  shows  this  system  and  Fig.  10  illustrates  a  bait  valve 
plunger  slurry  pump  which  was  manufactured  "by  t£e:Bci3icl  £of 
Its  action  is  similar  to  that  of  other  pumps  and  is  evident  from  the 
cut.  Recently  centrifugal  pumps  have  come  into  extensive  use 
for  moving  wet  materials  and  they  are  perhaps  best  for  this  pur- 
pose. They  are  used  at  the  lola  Portland  Cement  Company's 
plant  for  moving  the  slurry  of  the  "semi-dry"  process. 

Mixing  the  Raw  Materials. 

In  mills  using  the  dry  process,  the  raw  materials  go  from  the 
quarry  to  a  stone  house.  Here  they  are  treated  in  one  of  four 
ways : 

1.  This    method    is    applicable    only    to    cement-rock    which 
is   dumped   directly    into    large    piles,    which   are   then    analy- 
zed, and  from  this  analysis  the  necessary  limestone  or  clay  to  be 
added  is  calculated.     The  rock  is  then  loaded  on  buggies  or  bar- 
rows and  wheeled  to  the  crusher  after  being  weighed,  where  it 
meets    another    buggy  or    barrow    loaded  with  the    calculated 
amount  of  limestone  or  clay.     The  two  barrows  are  then  dumped 
into  the  crusher  together,  or  one  after  the  other.     In  some  mills 
using  cement-rock  and  limestone  of  nearly  the  same  composition 
the  materials  are  not  even  weighed  before  being  dumped  and  the 
barrows  are  merely  averaged  as  holding  so  much.     The  propor- 
tions being  roughly  made  somewhat  in  this  manner,  two  barrows 
of  rock  to  one  barrow  of  limestone,  etc.  This  system  of  mixing  is 
only  applicable  to  cement-rock  and  limestone  and  is  not  now  con- 
sidered very  satisfactory  even  for  these  materials  on  either  the 
score  of  satisfactory  mixing  or  economy  of  l^ndling, — the  former 
from  the  obvious  difficulty  of  sampling  such  an  irregular  material 
as  cement-rock  and  the  latter  because  of  the  extra  handling  of 
the  rock  and  limestone. 

2.  The  cement-rock  or  limestone  may  be  weighed  as  it  comes 
from  the  quarry  and  the  proper  amount  of  limestone  or  clay,  as 
calculated  from  quarry  analysis,  added.     Part  of  the  cars  are  then 


102  PORTLAND  CEMENT 

dumped  into  the  crusher  and  the  others  are  dumped  into  a  pile 
for  night,  \yhen.  it  is  necessary  to  wheel  from  these  to  the  crusher 
with  barrows/  etc.     At  several  mills  all  the  cars  are  dumped  into 
the;  cosher;  part  of  the  stone  going  to  the  mill  and  part  of  it 
being1  stored  In'  bins  for  the  night.     The  rock  is  drawn  from  the 
bins  upon  belt  conveyors  running  to  the  mill.     In  this  system, 
if  part  of  the  stone  is  dumped  into  piles  there  is  against  it  the 
extra  handling.     If  the  materials  are  limestone  and  clay  and  they 
are  dumped  into  a  pile  the  two  are  liable  to  separate  the  clay 
remaining  at  the  center  of  the  pile  and  the  limestone  rolling  to 
the  edges  with  the  result  that  when  the  pile  is  attacked  the  lime- 
stone is  first  obtained  and  then  the  clay.     This  of  course  gives 
a  very  irregular  mix.     When  the  mixture  of  limestone  and  clay 
is  dumped  into  the  bin  the  same  separation  takes  place  and  the 
result  is  even  worse.     This  system  may  be  employed  for  lime- 
stone and  cement-rock,  although  even  here  some  separation   of   the 
materials  takes  place  in  both  the  pile  and  the  bin,  but  it  gives  a 
much  more  regular  mix  than  would  result  from  its  use  with  clay 
and   limestone.     Generally   speaking   it  is  never   satisfactory  to 
dump  a  mixture  of  two  dissimilar  materials  into  a  large  bin  un- 
less the  mixture  is  first  granulated. 

3.  The  rock  is  dumped  into  the  crusher  and  conveyed  into 
bins,  where  it  remains  until  the  bins  are  analyzed,  when  it  is 
drawn  out  and  mixed  with  a  proper  amount  of  crushed  limestone 
or  clay  held  in  another  bin.     This   system  is  pretty  generally 
employed  by  mills  using  limestone  and  clay  or  shale.     The  only 
objection  to  it  is  the  difficulty  of  accurately  sampling  limestone 
and  shale  when  in  large  pieces  and  of  irregular  composition.     If 
the  materials  are  fairly  regular  in  chemical  composition,  how- 
ever, this  system  always  has  given  good  results  as  regards  the 
uniformity  of  the  cement  and  it  is  a  very  economical  way  of 
handling  the  materials. 

4.  A  better  way  than  any  of  the  above,  is  to  pass  the  shale  and 
limestone  through  the  ball  mills  or  other  preliminary  grinders, 
store  in  separate  bins  of  6  or  more  hours  capacity,  analyze  each 
bin  and  then  make  the  mixture  of  the  two  accordingly.     This 


QUARRYING,    EXCAVATING,    ETC.,    OF    RAW    MATERIAL          IO3 

is  a  particularly  desirable  way,  in  the  case  of  a  clay  and  lime- 
stone mixture,  as  segregation  of  the  two  can  not  occur  after  mix- 
ing as  both  are  finely  ground  and  the  mixture  of  clay  and  lime- 
stone is  a  homogeneous  one.  An  advantage  this  system  has 
over  the  one  just  mentioned  is  that  it  is  much  easier  to  sample 
the  materials  accurately  either  by  hand  or  an  automatic  sampler 
when  in  a  partially  ground  condition  and  also  that  it  is  easier  to 
weigh  material  in  such  state  by  means  of  automatic  weighing 
machines,  none  of  which  will  satisfactorily  handle  limestone 
which  has  been  merely  crushed  by  means  of  a  gyratory  crusher. 
This  system  requires  at  least  three  bins  for  each  material,  one  of 
which  is  to  be  used  while  the  other  two  are  filled  and  analyzed 
respectively. 

A  modification  of  the  above  system  which  has  been  tried  and 
found  satisfactory  at  a  number  of  plants  consists  in  mixing  the 
raw  materials  before  or  after  being  crushed  in  such  a  manner 
that  the  composition  is  slightly  higher  in  lime  than  is  desired. 
This  mixture  is  then  passed  through  the  ball  mills  or  other  pre- 
liminary grinders  and  into  steel  bins  holding  several  hours'  run. 
The  material  is  automatically  sampled  as  passed  into  the  bins, 
and  when  the  bin  is  filled,  the  sample  is  analyzed  and  the  small 
amount  of  dried  and  ground  shale  or  clay  necessary  to  bring  the 
mixture  to  the  proper  composition  is  then  added.  Three  bins 
will  be  needed  for  the  mix  and  one  for  the  shale. 

Storage  of  the  Raw  Materials. 

The  mechanical  equipment  of  the  stone  house  usually  consists 
of  the  crushers  and  dryers.  The  former  are  of  the  gyratory  rock- 
breaker  form,  which  will  be  described  in  the  next  chapter.  For- 
merly the  general  practice  at  the  older  mills,  even  the  large  ones, 
was  to  use  several  small  crushers  in  place  of  one  large  one. 
Now  most  of  the  newer  plants  are  employing  a  large  gyratory 
crusher  followed  by  two  or  more  smaller  ones.  At  the  plant  of  the 
Tidewater  Portland  Cement  Co.,  Union  Bridge,  Md.,  the  crushing 
of  the  limestone  will  be  done  by  a  No.  9  gyratory  crusher  followed 
by  two  No.  6*/2  crushers.  The  large  crusher  is  set  high  up  on  a 


IO4  PORTLAND  CEMENT 

solid  concrete  foundation  and  the  rock  is  led  by  spouts  from  it 
into  the  two  smaller  crushers.  The  cars  are  of  course  dumped 
directly  into  the  large  crusher,  the  opening  of  which  will  take  the 
largest  stones  ordinarily  handled  by  a  steam  shovel. 

After  crushing  the  rock  may  be  either  stored  or  dried.  When 
the  rock  is  stored  in  piles  uncrushed  as  it  comes  from  the  quar- 
ries, it  always  passes  direct  from  the  crushers  into  the  dryers,  in 
which  case  no  bins  are  usually  placed  above  the  dryers  and  the 
rock  is  fed  to  the  dryers  as  it  comes  from  the  crusher,  by  means 
of  a  bucket  elevator  or  a  belt  conveyor. 

When  the  rock  is  to  be  stored  in  bins  after  crushing,  this  stor- 
age may  be  done  either  before  or  after  drying.  With  some 
materials  clay  for  instance  and  some  shales,  drying  must  always 
come  before  storage.  If  this  is  not  done,  the  more  or  less  damp 
materials  will  pack  in  the  bins  and  can  not  be  drawn  out  of  them 
by  means  of  spouts. 

The  storage  bins  may  be  of  wood,  steel  or  concrete,  preferably 
the  latter.  When  wood  is  used,  this  has  to  be  braced  from  the 
inside  and  these  wooden  braces  often  are  worn  away  by  the  rock 
sliding  over  them  and  even  broken  by  the  weight  above  them. 
Wood,  while  cheaper  in  first  cost,  is  unquestionably  the  most  ex- 
pensive in  the  long  run  and  indeed  from  the  fire  risk  no  longer 
should  be  considered  in  the  construction  of  plants  which  re- 
present an  investment  of  a  million  or  more  dollars.  Circular 
steel  tanks  may  be  used  for  stone  storage  and  are  so  used  at  a 
number  of  plants.  If  the  bins  are  low  in  height,  the  storage 
capacity  is,  compared  to  the  cost  of  construction,  high  and  if  the 
bins  are  tall  the  pressure  on  the  bottom  material  when  the  bin 
is  full  is  great  and  hence  the  material  is  likely  to  pack  and  wedge 
and  consequently  not  flow  readily  from  the  bin.  At  the  plant  of 
the  El  Paso  Portland  Cement  Co.,  El  Paso,  Texas,  tall  octagonal 
reinforced  concrete  bins  are  used  for  rock  storage. 

By  far  the  best  construction  for  the  stone  store-house  is  con- 
crete and  steel.  The  walls  of  the  store-house  should  be  of  con- 
crete and  these  may  be  either  made  thick  with  a  slight  taper  from 
the  bottom  or  thinner  and  buttressed  sufficiently  to  stand  the 


QUARRYING,    EXCAVATING,    ETC.,    OF    RAW    MATERIAL          IO5 

pressure  of  the  stone.  The  roof  trusses  may  be  made  to  rest 
directly  on  the  bin  walls  while  the  belt  conveyors  for  bringing  in 
the  stone  are  carried  in  the  trusses. 

Whether  the  bins  are  of  steel,  concrete  or  wood  the  materials 
are  usually  drawn  out  of  them  by  means  of  a  tunnel  running 
under  them.  The  bottom  of  the  bin  should  have  openings  con- 
trolled by  slides  at  frequent  intervals  and  spouts  should  lead  from 
these  on  to  a  belt  conveyor  in  the  tunnel.  Fig.  n  shows  a  good 


Fig.  ii. — Good  form  of  raw  material  storage. 

arrangement  for  a  stone-storage  house.     The  walls  are  of  con- 
crete and  the  roof  trusses  of  steel. 

At  the  plant  of  the  Edison  Portland  Cement  Company  the  walls 
of  the  stone-storage  are  formed  of  sloping  triangular  shaped 
banks  of  earth  on  which  the  roof  trusses  rest.  The  outer  slopes  are 
turfed  and  serve  to  drain  off  the  water  while  the  inner  ones, 
which  are  lined  roughly  with  stones  between  which  no  mortar 
is  used,  serve  to  form  a  hopper  bottomed  bin.  The  cement-rock 


IO6  PORTLAND 

is  drawn  out  by  means  of  spouts  and  belt  conveyors  running  in  a 
tunnel. 

The  stone-storage  house  should  in  most  cases  hold  enough  of 
both  materials  to  keep  the  mill  running  for  three  days  without 
necessitating  shoveling  the  rock  from  that  portion  of  the  bins  not 
emptied  by  gravity.  The  stone  house  may  be  either  divided  into 
bins  or  not  as  the  material  requires,  but  the  shale  or  clay  must  al- 
ways be  kept  separate  from  the  limestone  when  these  materials 
are  used.  When  it  is  found  more  satisfactory  to  divide  the  stone- 
storage  into  bins,  this  may  be  done  by  means  of  concrete  walls 
or  wooden  partitions.  These  latter  may  be  kept  in  place  by  steel 
columns,  resting  in  concrete  footings  and  braced  by  steel  channels. 
Bins  in  the  store  house  are  not  necessary  except  when  the  method 
of  making  the  mix  is  that  outlined  previously  as  No.  2.  It  will 
generally  be  found  cheaper  and  always  better  to  follow  the  plan 
outlined  in  methods  No.  3  and  4. 

Weighing  the  Raw  Materials. 

In  some  instances  the  weighing  from  bins  is  done  by  means 
of  hopper  scales.  These  of  course  require  the  constant  care  of 
an  attendant  who  controlls  the  filling  and  emptying  of  the  scale 
hopper  by  means  of  a  door  in  the  bottom  of  the  latter  and  slides 
on  the  bottom  of  the  clay  and  limestone  bins.  Usually  these 
materials  are  not  run  directly  into  the  scale  hopper  from  the  large 
storage  bins  but  first  conveyed  into  smaller  bins  located  above 
the  scale  hopper,  and  from  these  bins  the  material  flows  into  the 
hopper  by  means  of  a  spout  and  is  stopped  at  will  by  a  slide  or 
gate.  These  hopper  scales  are  usually  provided  with  two  beams 
one  for  limestone  and  one  for  shale  or  clay.  These  scales  are 
fixed  so  that  the  beams  may  be  locked  in  a  box  and  only  the 
pointers  appear.  The  chemist  sets  the  poise  on  each  beam  with 
the  weight  of  that  material  desired  and  locks  the  case  so  that  the 
weight  can  not  be  altered.  As  the  limestone  or  shale  is  run  into 
the  hopper  the  operator  turns  the  key  of  the  beam  assigned  to 
whichever  is  being  weighed  and  continues  to  run  in  the  material 
until  the  beam  balances,  when  the  flow  of  material  is  stopped  by 
means  of  the  gate  or  slide.  Sometimes  this  is  done  automatically 


QUARRYING,    EXCAVATING,    ETC.,    OF    RAW    MATERIAL          IO7 

by  means  of  an  electrical  device  attached  to  the  beam.     One 
material  is  of  course  added  after  the  other. 

Automatic  scales  are  now  coming  into  use  at  the  newer  plants 
for  weighing  the  two  components  of  the  mix.  In  each  case  a 
pair  of  these  scales  are  employed,  one  for  each  material,  and  the 
two  scales  are  so  fixed  that  no  matter  which  fills  first  they  will 
dump  simultaneously.  All  forms  of  these  automatic  scales  are 


Fig.  12. — Avery  tandem  automatic  scales  for  raw  materials. 

delicate  and  somewhat  liable  to  get  out  of  order  but  they  do  away 
with  manual  labor  and  hence  lower  manufacturing  costs. 

Fig.  12  shows  a  pair  of  Avery  tandem  automatic  scales.  These 
scales  are  used  at  the  plant  of  the  Tidewater  Portland  Cement 
Co.,  not  only  for  weighing  the  raw  materials  but  also  for  weigh- 
ing clinker,  cement,  coal,  etc.  Other  makes  of  automatic  scales 
employed  in  cement  plants,  are  the  Richardson  scales  and  those 
of  the  Automatic  Weighing  Machine  Co.  Sometimes  automatic 


IO8  PORTLAND  CEMENT 

scales  are  mounted  on  a  movable  carriage  so  that  they  can  be 
shifted  under  any  one  of  a  series  of  bins,  but  usually  they  are 
fixed  in  one  place  and  the  material  brought  to  them  by  means  of 
a  screw  conveyor.  This  may  discharge  directly  into  the  scale 
or  else  into  a  small  bin  above  the  scale.  If  the  former  plan  is 
followed,  the  conveyor  should  be  continued  beyond  the  scale,  so 
that  the  material  not  taken  by  the  scale  (as  happens  when  the 
scale  dumps)  can  be  dropped  into  a  suitable  elevating  and  con- 
veying device  to  be  carried  back  into  the  bin  from  which  it  came. 

These  scales  not  only  serve  to  accurately  mix  two  materials 
but  also  to  keep  account  of  the  total  quantity  of  stone,  etc.  em- 
ployed. They  should  be  frequently  checked  as  to  the  accuracy 
of  the  weight  and  watched  to  see  that  they  dump  together. 

The  mix  may  be  dumped  directly  into  a  hopper  under  the 
scales  and  from  this  passed  to  a  screw  conveyor  leading  to  the 
stock  boxes  above  the  pulverizing  mills.  Sometimes  a  paddle  or 
cut-flight  conveyor  is  used  as  a  mixer.  At  the  plant  of  the  River- 
side Portland  Cement  Co.,  Riverside,  Cal.,  a  tube  mill  without 
pebbles  and  provided  with  angle  irons  is  used  as  a  mixer.  At 
other  plants  a  mixer  made  somewhat  similar  to  the  pug  mill, 
shown  in  Fig.  8,  except  that  the  shafts  around  which  the  peddles 
revolve  are  mounted  side  by  side  instead  of  one  under  the  other, 
is  employed.  No  water  is  of  course  added,  however.  Generally 
speaking,  25  or  30  feet  of  screw  conveyor,  particularly  if  this 
is  large  and  paddle  or  cut  flight  conveyors  are  used,  will  serve  to 
mix  the  material  thoroughly  enough  for  this  stage,  the  final  in- 
timate mixing  being  done  during  the  pulverizing. 

Dryers. 

The  dryers  used  for  drying  all  cement  raw  materials  may  be 
classed  under  two  heads — direct  fired  driers  and  waste  heat 
dryers.  The  former  are  heated  by  means  of  a  fire  box  at  one  end 
of  the  dryer  or  by  an  oil  spray  and  the  latter  by  the  hot  waste 
gases  from  the  rotary  kilns.  With  both  forms  the  rock  is  fed 
in  at  the  upper  end  and  works  its  way  out  at  the  lower. 

Direct  fired  dryers  (Fig.  13)  are  cylindrical  in  shape,  from 
4  to  5  feet  in  diameter  and  from  40  to  60  feet  in  length.  They 


QUARRYING,    EXCAVATING,    ETC.,    OF    RAW    MATERIAL          IOO, 

are  similar  in  construction  to  the  rotary  kiln  described  in  chapter 
VII.  They  are  inclined  from  the  horizontal  at  a  pitch  of  from 
l/2  to  24  mcn  to  the  foot  and  are  usually  provided  with  angle  or 
channel  irons  bolted  to  the  inside  to  act  as  shelves  to  carry  the 
rock  up  and  expose  it  to  the  hot  gases.  (See  Fig.  14.)  Some 
of  them  have  their  upper  half  divided  into  four  compartments  by 
means  of  plates  in  order  to  expose  a  greater  surface  of  rock 
(See  Fig.  15.)  One  direct  fired  dryer  60  by  5  ft.  will  take  care 
of  about  500  to  700  tons  of  cement-rock  or  limestone  in  24  hours, 
depending  of  course  on  the  moisture  in  these  materials.  These 


Fig.  14.— Rotary  dryer  shelver.  Fig.  15.— Rotary  dryer  compartments. 

dryers  will  evaporate  from  4  to  5  Ibs.  of  water  per  pound  of  coal, 
in  drying  cement-rock  or  limestone. 

The  waste  heat  dryers  are  the  invention  of  Mr.  Chas. 
A.  Matcham  of  Allentown,  Pa.  They  may  be  considered 
as  the  latest  device  for  increasing  the  economy  of  the  rotary  kiln 
by  utilizing  its  waste  gases  for  drying.  These  dryers  are  similar 
in  every  respect  to  the  ordinary  direct  fired  dryer  described 
above  except  that  they  are  made  somewhat  larger  and  have  no 
fire  box.  The  arrangement  with  reference  to  the  kiln  is  shown 
in  Fig.  1 6.  The  dryers,  as  will  be  seen  from  this,  are  immediately 
back  of  and  in  a  line  with  the  kilns,  so  that  they  can  receive  the 
waste  gases  of  the  latter  with  as  little  impediment  to  the  draft  as 


no 


PORTLAND  CEMENT 


possible.  Between  the  dryers  and  kilns  is  the  customary  dust- 
chamber  (see  chapter  VII)  and  on  this  rests  a  stack  provided 
with  a  damper.  When  the  dryers  are  in  use  this  damper  is 
closed  and  the  kiln  stack  is  not  used,  all  the  gases  from  the  kiln 
passing  through  the  dryer.  As  the  gases  from  a  125  ft.  rotary 
kiln  are  at  about  900-1000°  F.  and  there  are  at  least  150,000 
B.  t.  u.  (=  II  Ibs.  of  coal)  in  the  gases  entering  the  dryer 
per  minute  no  difficulty  is  experienced  in  drying  large  quantities 
of  material  very  thoroughly  by  means  of  these  waste  heat  dryers. 
There  is  usually  a  movable  housing  between  the  dryers  and  dust- 


Fig.  16.— Dryer  arranged  to  utilize  waste  heat  from  kilns. 

chamber  to  allow  easy  access  to  the  former  for  repairs  without 
shutting  down  the  kiln.  The  stone  from  the  dryer  drops  down 
through  an  opening  in  the  housing  into  a  pit,  from  which  it  is 
elevated  to  the  storage  or  stock-bins  by  means  of  bucket  elevators. 
In  order  not  to  effect  the  capacity  of  the  kilns,  these  dryers  must 
be  of  large  diameter  and  must  be  provided  with  taller  stacks  than 
are  ordinarily  employed  for  kilns  or  direct  fired  dryers. 

These  waste  heat  dryers  save  the  coal  used  in  heating  the 
ordinary  direct  fired  dryers  and  also  the  labor  necessary  to  stoke 
them.  This  saving  in  the  cost  of  manufacture  approaches  one- 


QUARRYING,    EXCAVATING,    ETC.,    OF    RAW    MATERIAL         III 

half  to  one  cent  per  barrel,  depending  upon  the  moisture  in  the 
raw  materials  and  the  cost  of  coal.  The  waste  heat  dryers  also 
dry  very  thoroughly,  and  sometimes  even  break  down  the  struc- 
ture of  the  rock,  clue  to  the  high  temperature  of  the  gases  pass- 
ing through  them,  thus  often  effecting  a  saving  in  the  cost  of 
pulverizing. 

Sometimes  in  drying  clay,  this  latter  balls  up  in  the  dryer.  The 
outside  of  these  clay  balls  bake  hard  but  the  inside,  even  after 
they  have  passed  through  the  hottest  part  of  the  dryer,  remains 
wet.  In  drying  such  clays,  therefore,  it  is  found  most  successful 
to  do  the  drying  in  two  stages,  first  passing  the  clay  through  a 
dryer,  then  through  a  set  of  rolls  or  other  disintegrator  to  break 
open  these  balls  and  allow  the  heat  to  get  at  the  moisture  and 
finally  through  a  second  dryer  in  which  the  moisture  remaining 
in  the  center  of  the  lumps  is  driven  off.  The  clays  along  the 
Hudson  river  used  by  the  Alsen  and  other  plants  there  are  very 
plastic  and  ball  up  and  bake  this  way.  Here  this  system  of  dry- 
ing ^  has  proved  very  efficient. 

Clays  often  contain  considerable  moisture  and  when  this  is  the 
case  much  coal  is  necessary  to  dry  them,  hence  waste  heat  dry- 
ers will  here  often  effect  a  great  saving  over  direct  fired  dryers. 
Slag  which  has  been  granulated  by  water,  as  is  always  done  when 
this  material  is  used  for  Portland  cement,  is  particularly  hard 
to  dry  and  the  expense  of  drying  granulated  slag,  often  carry- 
ing as  much  as  20  per  cent,  water,  almost  balances  the  fact  that 
it  is  a  waste  product  and  may  be  obtained  for  nothing  by  the 
companies  using  it. 

Of  late  years,  a  number  of  attempts  have  been  made  to  dry 
marl  and  manufacture  cement  from  this  by  the  dry  process.  So 
far  the  attempt  does  not  seem  to  have  been  very  successful  and 
at  any  rate  none  of  the  older  companies  originally  installing  the 
wet  process  have  thought  well  enough  of  the  dry  process  to 
make  the  change.  When  the  marls  are  more  or  less  dry,  as  they 
often  are  when  not  dredged  from  under  water,  the  waste  heat 
dryers  will  undoubtedly  open  up  a  way  for  the  economic  applica- 
tion of  the  dry  process  to  this  material.  In  the  new  plant  of  the 
Norfolk  Portland  Cement  Co.,  Berkeley,  Va.,  the  dry  process  will 


112  PORTLAND  CEMENT 

be  employed  upon  such  a  marl  with  direct  fired  dryers,  however, 
to  drive  off  the  moisture  from  the  marl. 

The  thoroughness  with  which  the  marl  is  dried  has  a  con- 
siderable bearing  upon  the  ease  with  which  the  material  can  be 
ground.  The  attempt  to  grind  damp  materials  always  results  in 
decreasing  the  output  of  the  grinding  machinery.  With 
ball  mills,  Fuller  mills,  Griffin  mills,  (see  Chapter  VI)  and  other 
screen  mills  the  steam  driven  off  from  the  damp  stone  and  clay 
by  the  heat  produced  in  grinding  stops  up  the  screens,  while 
with  tube  mills  the  pebbles  often  coat  with  damp  and  consequent- 
ly sticky  material.  Usually  the  dryer  the  material,  the  more 
efficiently  it  can  be  pulverized,  and  coal  burnt  in  drying  is  coal 
saved  in  pulverizing.  A  good  dryer  when  not  forced  beyond  its 
capacity  should  reduce  the  moisture  in  any  class  of  material  to 
one  or  two-tenths  of  a  per  cent. 

Wet  Process. 

The  marl  is  usually  received  at  the  mill  whether  it  comes  by 
cars,  barge  or  pipe  line  in  the  form  of  a  thin  mud.  After  remov- 
ing roots,  sticks,  stones,  etc.,  this  wet  marl  is  stored  in  large  con- 
crete basins  or  steel  tanks.  The  clay  is  usually  dried  to  facilitate 
the  chemical  work  of  obtaining  a  proper  mixture,  and  dis- 
integrated in  edge  runner  mills  or  dry  pans.  From  the  storage 
tank  the  marl  is  pumped  either  into  a  tank  of  known  volume  or 
the  hopper  of  a  scale.  The  clay  is  elevated  to  bins  above  this 
and  mixed  as  directed  by  the  chemist.  From  the  measuring  tank 
or  scales,  the  mixture  is  dumped  into  a  "pug"  mill  and  thoroughly 
mixed.  From  the  pug  mill  the  mass  is  run  into  large  vats  where 
it  is  sampled  and  analyzed.  If  of  correct  composition,  it  is 
passed  on  for  final  grinding,  if  not,  the  required  quantity  of  marl 
or  clay,  as  the  case  may  be,  is  added.  There  should  be  three  or 
more  of  these  vats  so  that  one  may  be  filling,  one  analyzed,  and 
the  third  emptied  all  at  the  same  time.  These  vats  are  provided 
with  stirrers  so  as  to  keep  the  mass  in  constant  agitation  to  pre- 
vent any  part  of  it  setting  out  and  also  to  mix  in  thoroughly  any 
clay  or  marl  that  may  be  added  here  to  correct  the  mix.  Com- 
pressed air  is  also  used  for  agitating  the  contents  of  the  slurry 
tanks  in  place  of  the  revolving  arm  with  paddles. 


QUARRYING,    EXCAVATING,    ETC.,    OF    RAW    MATERIAL         1 13 

Agitators  of  the  propeller  form  are  also  used,  in  which  the 
shaft  is  horizontal  instead  of  vertical  and  about  which  blades  are 
fixed. 

As  dredged  from  the  deposit,  the  marl  contains  from  40  to  50 
per  cent,  water,  which  is  usually  increased  in  the  pug  mills,  in 
order  to  facilitate  pumping  it  from  one  part  of  the  mill  to  another, 
so  that  the  slurry  usually  contains  from  60  to  65  per  cent,  of 
water.  Various  mechanical  means  have  been  proposed  for  ex- 
tracting the  moisture  from  the  slurry.  The  following1  is  a  list 
of  these: 

1.  Hydraulic  filter  presses. 

2.  Perforated  belts  passing  between  rolls  which  press  out  the 
moisture. 

3.  Large  wheels  with  wide  perforated  faces  between  which  the 
material  is  pressed  as  it  passes  through. 

4.  Steel  tank  lined  with  porous  tile  and  air  pressure  applied, 
forcing  the  water  through  tile,  and  tank  is  then  drained. 

It 'seems  doubtful,  however,  if  any  of  these  mechanical  means 
will  succeed  because  of  the  fine  state  of  subdivision  in  which  the 
marl  and  clay  exist  in  the  slurry.  At  the  present,  therefore,  the 
only  way  of.  getting  rid  of  this  excess  of  water  is  by  evapora- 
tion. At  one  or  two  plants  as  previously  remarked  the  attempt 
has  been  made  to  dry  the  marl  in  dryers  similar  to  those  used 
for  dry  materials,  such  as  cement-rock,  and  to  use  a  dry  process. 
The  general  plan,  however,  now  seems  to  be  to  dry  the  slurry  in 
the  upper  part  of  the  rotary  kiln  during  burning,  making  burning 
and  drying  one  operation.  This  is  no  doubt  in  part  due  to  the 
fact  that  the  wet  process  offers  much  better  facilities  for  making 
an  accurate  mixture  of  these  two  materials  than  does  the  dry  one. 
There  has  been  no  increase  in  the  production  of  Portland  cement 
from  marl  and  clay  by  the  wet  process  since  1905  and  indeed  the 
last  few  years  have  actually  seen  a  decrease  due  no  doubt  to  the 
fact  that  a  number  of  mills  using  marl  and  clay  have  substituted 
limestone  for  the  former. 

Semi-Wet  Process. 
This  process  is  sometimes  called  the  "semi-dry"  process.     Both 

1  Soper— Cement  and  Engineering  News,  Feb.,  1904. 

8 


114  PORTLAND  CEMENT 

names  are  misnomers  as  about  as  much  water  is  present  in  the 
slurry  of  this  process  as  in  that  of  the  wet  process.  What  the 
semi-wet  or  semi-dry  process  really  amounts  to,  is  a  wet  or 
slurry  process  applied  to  dry  materials. 

This  process  is  used  by  the  Tola  Portland  Cement  Co.,  the  Ash 
Grove  Portland  Cement  Co.,  the  Texas  Portland  Cement  Co.,  the 
Dixie  Portland  Cement  Co.,  and  the  plants  of  the  United  Kansas 
Portland  Cement  Company.  This  process  consists  in  passing 
the  pulverized  limestone  and  shale  as  they  come  from  the  mills 
through  pug  mills  in  which  they  are  mixed  with  water.  From 
the  pug  mill  the  mixture  or  slurry  goes  to  tanks  where  it  is 
thoroughly  agitated  and  mixed.  The  different  tanks  holding 
this  slurry  are  analyzed  and  when  the  contents  of  one  of  them  is 
found  to  be  not  of  the  desired  chemical  composition,  a  correction 
is  made  by  adding  the  proper  quantity  of  clay  or  limestone  as 
the  case  may  require.  The  slurry,  after  its  chemical  composition 
has  proved  satisfactory  is  fed  into  the  kilns  and  burned,  just  as 
with  the  wet  process. 

The  idea  of  the  semi-wet  process  is  that  it  gives  a  more 
intimate  mixture  of  the  two  raw  materials  than  is  -possible  with 
the  dry  mixture.  This  is  true  where  the  raw  materials  are  not 
finely  ground,  but  where  the  materials  have  been  pulverized  so 
that  95  per  cent,  of  the  mixture  will  pass  through  the  No.  100 
mesh  sieve  it  has  been  proved  that  just  as  satisfactory  cement 
can  be  manufactured  by  the  dry  process  as  by  the  semi-wet 
process.  The  semi-wet  process  was  originally  developed  in  this 
country  at  plants  using  natural  gas  for  fuel  and  consequently 
the  water  to  be  driven  oft0  in  the  kiln  did  not  have  to  be  con- 
sidered owing  to  this  cheap  fuel.  Where  coal,  however,  has 
to  be  used  to  burn  the  slurry,  it  is  unquestionably  very  much 
more  economical  and  just  as  satisfactory  to  grind  the  raw 
materials  finer  and  use  the  dry  process,  as  very  much  less  coal 
is  required  to  grind,  particularly  with  the  improved  grinding 
machinery  at  the  present  time  obtainable,  than  would  be  required 
to  drive  off  the  water  in  the  slurry.  In  the  semi-wet  process 
however,  as  with  the  wet  process,  it  is  easier  to  control  the  com- 


QUARRYING,    EXCAVATING,    ETC.,    OF    RAW    MATERIAL         11$ 

position  and  there  is  also  said  to  be  less  dust  from  kilns  operating 
upon  wet  mixtures. 

Examples  of  Treatment  of  Raw  Materials  at  Different  Mills. 

Below  will  be  found  short  descriptions  of  methods  employed 
at  some  of  the  more  successful  Portland  cement  mills  for  mix- 
ing and  preparing  the  raw  material  for  the  final  grinding. 

Dry  Process  Mills. 

DEXTER  PORTLAND  CEMENT  Co. — Raw  Materials,  Cement-Rock 
only.  Cement-rock  is  quarried,  loaded  on  side  dump  cars  and 
hauled  to  mill  on  incline  railway.  Mix  is  regulated  by  properly 
distributing  cars  between  portions  of  quarry  where  the  rock  is 
high  and  low  in  lime,  respectively.  When  necessary  the  small 
amount' of  clay  or  limestone  required  to  adjust  the  composition  is 
added  at  the  crusher.  Rock  is  crushed  in  a  Gates  crusher  and 
divided,  part  of  crushed  rock  going  to  the  mill  and  part  into  bins 
for  the  night.  Rock  is  dried  in  rotary  dryer  just  before  going 
to  ball  mills.  Bins  are  tapped  below  at  night  and  crushed  rock 
sent  to  mill  on  belt  conveyor. 

NAZARETH  PORTLAND  CEMENT  Co. — Raw  Materials,  Cement- 
Rock  only.  Stone  loaded  at  the  face  by  hand  into  three-ton  cars 
and  run  by  gravity  from  this  point  to  the  bottom  of  an  incline  plane 
leading  to  the  mill.  It  is  then  hoisted  to  the  top  of  the  plane  at 
which  point  crushers  are  located  and  the  rock  dumped  into  the 
same.  Mixture  is  made  in  the  quarry  by  properly  working  the 
same  with  regard  to  high  and  low  stone.  From  the  crusher  the 
rock  is  passed  into  storage  and  from  this  through  a  hammer 
mill.  When  clay  is  necessary  to  properly  adjust  the  composition 
it  is  added  after  the  rock  passes  through  this  mill. 

LAWRENCE  CEMENT  Co. — Raw  Materials,  Cement-Rock  and 
Limestone.  Cement-rock  and  limestone  are  quarried  and  loaded 
on  dump  cars  by  hand.  Both  materials  are  crushed  and  dried 
separately,  elevated  into  hopper-shaped  bins  and  stored  separately. 
Analyses  are  then  made  and  the  contents  of  the  bins  mixed  in 
proper  proportions  and  conveyed  to  the  ball  mills. 


Il6  PORTLAND  CEMENT 

ALSEN'S  AMERICAN  PORTLAND  CEMENT  Co. — Raw  Materials, 
Limestone  and  Clay.  Limestone  is  quarried,  loaded  on  cars, 
crushed  in  a  No.  8  Austin  Crusher.  After  this  it  is  run  through 
a  revolving  screen  and  all  stone  which  will  not  pass  through 
a  2  inch  ring  is  recrushed  in  two  No.  5  Gates  crushers — all  of 
which  are  located  at  the  quarry.  Crushed  material  is  sent  to 
mill  by  cars,  where  it  is  dried  in  waste  heat  dryers  and  then 
broken  down  by  means  of  ball  mills  provided  with  perforated 
plates  but  without  screens.  After  leaving  the  ball  mills  it 
passes  into  the  mixing  bins,  when  clay  is  added.  Clay  is  passed 
through  a  disintegrator,  two  rotary  waste  heat  dryers,  another 
disintegrator  and  then  through  two  Matcham  dryers,  after  which 
it  is  added  to  the  limestone  in  proper  proportion.  The  mixture  is 
ground  on  Fuller-Lehigh  pulverizers. 

VULCANITE  PORTLAND  CEMENT  Co. — Razv  Materials,  Cement- 
Rock  and  Limestone.  Cement-rock  is  quarried,  loaded  on  skips 
by  hand,  conveyed  to  the  mill  by  aerial  hoist,  where  it  is  sampled 
and  dumped  in  piles.  The  cement-rock  is  wheeled  on  barrows 
from  the  pile  to  the  crusher  where  the  proper  amount  of  lime- 
stone is  added.  The  mix  is  then  dried  in  rotary  dryers  and  sent 
to  the  mill  for  grinding. 

ST.  Louis  PORTLAND  CEMENT  Co. — Raw  Materials,  Limestone 
and  Shale.  The  limestone  is  quarried  coarsely  crushed  at  the 
quarry,  and  recrushed  by  No.  5  crushers  at  the  mill.  The  shale 
on  arrival  at  the  mill,  passes  through  a  disintegrator,  after  which 
it  is  dried  in  rotary  dryers  and  stored  in 'bins.  The  fine  lime- 
stone is  dried  in  rotary  dryers  and  stored  in  bins.  The  two  are 
then  mixed  and  pulverized. 

VIRGINIA  PORTLAND  CEMENT  Co. — Raw  Materials,  Limestone 
and  Shale.  The  limestone  is  crushed  in  the  quarry  by  a  No.  5 
Gates  crusher,  and  carried  to  the  mill  by  cars,  here  it  is  dried  in  a 
Ruggles-Coles  dryer,  ground  in  ball  mills  and  stored  in  a  large 
bin.  The  shale  is  dried,  passed  through  a  set  of  Buchanan  rolls 
and  then  ground  in  rock  emery  mills.  The  shale  is  then  stored  in 
a  set  of  five  bins  and  from  these  passes  to  a  bin  beside  the  lime- 
stone bin.  The  two  materials  are  then  mixed  in  proper  propor- 
tions and  ground  in  tube  mills. 


QUARRYING,    EXCAVATING,    ETC.,    OF    RAW    MATERIAL          1 1/ 

ALPHA  PORTLAND  CEMENT  Co.,  MILL  No.  2,  ALPHA,  N.  J. — 
Materials,  Cement-Rock  and  Limestone.  The  cement-rock 
is  quarried  and  hauled  up  an  incline  to  the  mill  where  the  proper 
amount  of  limestone,  as  determined  by  analysis  of  the  quarry 
drill  holes,  is  added.  The  mixture  is  then  crushed  in  a  Gates 
crusher,  dried  in  rotary  dryers,  and  finely  ground  in  Griffin  mills. 

TIDEWATER  PORTLAND  CEMENT  COMPANY  (Under  Construc- 
tion).— Raw  Materials,  Limestone  and  Shale.  The  limestone 
will  be  crushed,  dried  and  then  ground  in  ball  mills  provided  with 
perforated  plates  only.  The  limestone  will  pass  from  the  ball 
mills  into  three  steel  bins  holding  8  hours'  run  each.  The  contents 
of  the  steel  bins  will  be  analyzed  as  filled  and  the  clay  added  in 
proportions  which  the  analysis  shows  necessary.  The  mixture 
will  then  be  ground  in  Fuller-Lehigh  Mills.  The  shale  will  be 
crushed,  dried,  disintegrated,  passed  into  three  tanks  and  analyzed 
just  as  is  done  with  the  limestone  before  being  mixed  with  the 
latter.  As  the  quantity  of  material  analyzed  in  the  bins  is  small, 
it  will  be  possible  by  this  system  to  control  the  composition  of 
the  cement  within  very  close  limits.  The  weighing  will  be  done 
by  a  pair  of  Automatic  Scales,  one  of  which  will  be  used  for  the 
limestone  and  one  for  the  clay,  the  materials  being  dumped 
simultaneously  and  automatically.  The  sampling  will  be  done, 
as  the  bins  are  filled,  by  means  of  a  Meade  automatic  sampler 
(See  Chapter  XL). 

ALLENTOWN  PORTLAND  CEMENT  COMPANY. — Raw  Materials, 
Cement-Rock  and  Limestone.  The  limestone  is  crushed  first  with 
a  No.  9  crusher  and  then  with  two  No.  6  crushers,  passed 
through  two  waste  heat  dryers  and  into  a  bin.  The  limestone  is 
received  in  much  smaller  pieces  and  is  crushed  by  a  No.  6^2 
crusher,  dried  in  one  waste  heat  dryer  and  passed  into  a  bin.  At 
the  bottom  of  the  two  bins  are  gates  and  spouts  directly  opposite 
each  other.  Two  or  three  small  cars  of  about  I  cubic  yard 
capacity,  having  movable  partitions,  running  lengthwise  are 
mounted  on  wheels  so  that  they  can  be  moved  directly  underneath 
a  set  of  these  spouts.  The  partition  in  the  cars  is  regulated 
according  to  the  analysis  of  the  cement-rock,  so  that  when  these 
cars  are  filled,  one  side  with  limestone  then  the  other  side  with 


Il8  PORTLAND 

cement-rock,  the  proportions  between  the  two  sides  of  the  car 
will  be  that  of  the  limestone  and  cement-rock,  which  is  desired 
for  the  proper  composition  of  the  mix.  These  cars  are  arranged 
with  drop  bottoms  and  discharged  directly  on  to  a  belt  conveyor. 
This  latter  in  turn  dumps  into  an  elevator  which  carries  the 
material  directly  to  the  bins  over  the  ball  mill  in  the  raw  material 
building.  The  final  pulverizing  is  done  by  means  of  Fuller- 
Lehigh  mills. 

UNIVERSAL  PORTLAND  CEMENT  COMPANY,  PITTSBURG  MILL. — 
'Raw  Materials,  Limestone  and  Blast-Put -nace  Slag.  The  raw 
materials  are  received  at  the  mill  in  railroad  cars  and  dumped 
into  bins.  The  limestone  is  crushed  but  no  crushing  is  necessary 
for  the  slag.  Both  materials  are  dried  in  rotary  direct  fired 
dryers.  After  drying  the  limestone  and  slag  are  placed  in 
storage  bins  and  analyzed.  They  are  then  partially  ground  in 
ball  mills,  the  two  materials  being  kept  separate.  From  the  ball 
mills  the  materials  pass  to  the  hoppers  above  the  weighing 
machines.  These  are  automatic.  From  the  scales  the  materials 
are  conveyed  to  the  tube  mills  where  the  mixing  and  final 
pulverizing  are  done. 

Wet  Process  Mills. 

EGYPTIAN  PORTLAND  CEMENT  Co. — Razv  Materials,  Marl  and 
Clay.  Marl  is  dug  up  by  a  dipper  dredge  and  dumped  into  a 
stone  separator  on  a  scow  lashed  to  the  dredge,  from  the  separator 
it  is  transferred  to  barges,  which  convey  it  to  the  shore,  where 
they  are  unloaded  and  the  marl  pumped  to  the  mill  by  a  ball-valve 
Bonnot  slurry  pump.  At  the  mill  the  marl  is  received  in  two 
large  tanks  which  discharge  into  a  pug  mill.  The  clay  is  un- 
loaded on  the  floor  of  the  clay  house  and  ground  in  a  dry  pan, 
after  which  it  is  screened  and  elevated  to  a  bin  close  to  the  marl 
bin.  The  marl  and  clay  are  then  mixed  in  the  pug  mill  in  proper 
proportions,  passed  into  a  storage  tank,  ground  in  emery  mills, 
and  then  spouted  to  either  of  two  shallow  pits,  where  it  is  held 
for  analysis  and  corrected  if  necessary.  The  slurry  is  then 
pumped  through  the  tube  mills  for  the  final  grinding. 

BRONSON  PORTLAND  CEMENT  Co. — Razv  Materials,  Marl  and 
Clay.  Marl  is  excavated  by  a  dipper  dredge  mounted  on  a  scow, 


QUARRYING,    EXCAVATING,    ETC.,    OF   RAW    MATERIAL         1 19 

which  floats  in  the  channel  cut  by  the  dipper.  The  marl  is  carried 
to  the  mill  by  cars,  which  dump  into  pug  mills  made  to  act  also  as 
stone  separators.  From  these  the  marl  is  spouted  into  concrete 
storage  tanks,  where  it  is  analyzed  and  pumped  to  the  mixing 
floor.  The  clay  is  ground  in  edge  runner  mills  (or  dry  pans)  and 
from  these  elevated  to  a  bin  above  the  mixing  floor,  where  it  is 
added  to  the  marl,  in  the  amount  determined  by  analysis ;  after 
which  the  mixture  is  thoroughly  pugged,  the  pug  mills  discharg- 
ing by  gravity  into  tube  mills  where  the  final  grinding  takes  place. 

OMEGA  PORTLAND  CEMENT  Co. — Marl  and  Clay.  Marl  is 
dredged,  the  dipper  dropping  it  into  buckets  on  cars,  each  car 
carrying  two  buckets  and  each  bucket  of  one  cubic  yard  capacity. 
The  cars  are  hauled  to  a  trestle  or  trolley,  which  picks  up  the 
buckets  and  carries  them  into  the  wet  mill,  where  they  are  dis- 
charged into  a  stone  separator.  From  the  stone  separator  the 
marl  passes  into  vats  where,  after  thorough  agitation,  it  is  sam- 
pled and  analyzed.  It  is  then  pumped  into  three  yard  measuring 
cylinders,  the  proper  amount  of  clay  added  to  it,  and  the  mixture 
passed  through  a  pug  mill  to  the  tube  mills  for  final  grinding. 
Semi-Wet  Process  Mill. 

THE  DIXIE  PORTLAND  CEMENT  COMPANY. — Raw  Materials, 
Limestone  and  Shale.  Both  these_ materials  are  obtainable  near 
the  plant.  The  shale  is  conveyed  directly  from  the  mountain  side 
into  storage  tanks  by  a  belt  conveyor  2,200  feet  long.  The  lime- 
stone is  brought  from  the  quarry  in  cars  by  gravity  on  a  2  per 
cent,  grade.  When  empty  the  cars  are  carried  back  to  the  steam 
shovel  by  electric  hoisting  engines.  The  limestone  is  first  passed 
through  a  No.  18  crusher  and  from  this  to  two  No.  6  crushers. 
From  these  crushers  the  limestone  is  carried  by  belt  conveyors 
into  four  steel  tanks  of  300  tons  capacity  each.  The  shale  is 
crushed  and  stored  in  two  similar  tanks.  From  these  tanks  the 
stone  and  shale  are  delivered  by  chutes  at  the  bottom  on  to  a 
belt  conveyor  which  carries  the  material  to  dryers  and  then  to 
the  grinding  mills.  The  final  pulverizing  is  done  in  Griffith  mills 
after  which  the  material  is  mixed  with  water  in  two  pug  mills. 
From  the  pug  mills  the  slurry  is  passed  to  tanks  where  it  is 
thoroughly  agitated,  mixed,  analyzed  and  if  necessary  brought  to 
the  right  chemical  composition.  It  is  then  fed  to  the  kilns. 


Chapter  VI. 


GRINDING  THE  RAW  MATERIAL  AND  GRINDING 
MACHINERY. 

In  the  early  days  of  the  industry  when  the  plants  were  small, 
manufacturing  only  a  few  thousand  barrels  a  year  each,  both  the 
raw  rock  and  the  clinker  were  ground  with  mill  stones,  just  as 
corn  is  ground  in  the  small  water-power  mills  familiar  to  every 
one.  The  first  advance  upon  this  was  to  encase  the  stones,  and  as 
the  American  manufacturers  began  to  work  up  a  home  market  for 
their  product  and  to  increase  their  output  to  meet  the  demand, 
they  also  began  to  experiment  with  a  view  to  securing  more  effi- 
cient pulverizers  than  the  nrll  stones.  As  a  result  of  tfieir 
experiments,  the  Atlas  Portland  Cement  Co.  patented  the  Hunt- 
ington  mill  which  they  still  use.  In  1889  the  American  Cement 
Co.  installed  a  Griffin  mill  in  their  plant  at  Egypt  and  this  mill 
is  still  in  use  there,  and  in  many  other  large  plants  throughout 
the  country.  Another  system  of  grinding  consisting  of  a  ball 
mill  for  the  coarse  grinding  and  a  tube  mill  for  the  final  pul- 
verization was  introduced  about  this  time  by  the  Bonneville 
Cement  Co.  in  their  plant  at  Siegfried,  Pa.,  and  this  combina- 
tion also  has  come  into  prominent  use  in  the  industry.  The 
newest  pulverizer  to  be  introduced  to  any  extent  in  the  industry 
is  the  Fuller-Lehigh  mill.  This  was  first  used  at  the  plant  of 
the  Phoenix  Cement  Co.  in  1904.  This  mill  has  proved  a  very 
efficient  pulverizer  and  represents  a  forward  step  in  the  devel- 
opment of  pulverizing  machinery.  Other  mills  which  are  in 
use  to  some  extent  in  the  industry  are  the  Kent  mill  and  the 
Raymond  mill. 

At  the  plant  of  the  Edison  Portland  Cement  Co.,  at  Stewarts- 
ville,  N.  J.,  the  grinding  is  done  by  a  system  of  rolls  and  air 
separators.  The  rock  passes  in  a  solid  stream  through  the  rolls, 
undergoing  considerable  compression  as  it  does  so.  The  crushed 
material  is  then  dropped  in  front  of  revolving  fans  which  blow 


GRINDING  RAW    MATERIAL   AND   MACHINERY  121 

out  the  fine  particles  into  large  settling  chambers.  The  coarse 
material  rejected  by  the  fans  is  then  returned  to  the  rolls  by 
suitable  conveying  mechanism  for  further  reduction. 

In  the  use  of  any  of  the  above  mills  upon  dry  raw  materials 
it  is  necessary  to  break  up  the  material  to  a  size  which  will 
permit  the  material  to  be  fed  to  the  mills.  In  order  to  do  this,  as 
has  been  stated,  crushers  of  the  gyratory  type  are  usually  em- 
ployed, as  the  first  stage  in  this  preliminary  reduction.  This 
form  of  crusher  was  developed  by  the  Gates  Iron  Works,  Chicago, 
but  is  now  made  and  sold  by  several  firms.  The  jaw  or  Blake 
crusher  was  also  used  by  some  of  the  older  mills  but  is  not  suit- 
able to  crushing  the  large  quantities  of  rock  necessary  to  keep  a 
modern  cement  mill  in  operation.  The  gyratory  crusher  is  some- 
times followed  by  a  set  of  rolls  or  a  coffee  mill  crusher,  particu- 
larly where  Fuller-Lehigh  or  Griffin  mills  are  used  for  fine  grind- 
ing. The  hammer  mill  is  also  used  after  the  gyratory  crusher 
to  .prepare  material  for  pulverizers  of  this  type  and  also  for 
the  tube  mill. 

Below  will  be  found  descriptions  of  the  various  types  of  mills 
used  to  prepare  the  raw  materials  for  burning,  and  on  page  157 
will  be  found  a  table  showing  the  capacity  of  these  mills  and  the 
power  required  to  run  them. 

Gyratory  Crusher. 

Fig.  17  shows  a  section  of  a  gyratory  crusher.  Referring  to 
this  illustration,  on  the  spindle  g,  is  mounted  the  chilled-iron 
crushing  head  c.  The  hopper-shaped  top  shell  h  is  lined  with 
concave  chilled  plates.  The  crushing  is  done  in  the  annular 
space  between  the  chilled  surfaces. 

The  spindle  being  centrally  held  in  the  spider  at  the  top  rests 
at  its  lower  end,  passing  loosely  through  an  eccentric  driven  by 
bevels  b.  The  spindle  thus  receives  a  gyrating  motion  and  may 
or  may  not  rotate.  Thus,  one  point  in  the  annular  space  is  wide, 
while  a  point  opposite  is  narrow,  and  the  crushing  force  is  ob- 
tained on  account  of  the  head  approaching  and  receding  from  the 
concaves.  In  the  type  described  the  largest  motion  is  at  the 
bottom  where  the  annular  space  is  narrow,  and  this  motion  is 


122 


PORTLAND  CEMENT 


the  throw  or  stroke.  The  number  of  revolutions  of  the  spindle 
and  number  of  strokes  correspond,  generally  being  about  200  per 
minute.  On  a  crusher  having  an  annular  opening  at  the  top, 
10  in.  X  60  in.  circumference,  the  stroke  would  generally  be 


Fig.  17.— Gates  crusher. 

about  y%  inch.  These  machines  work  continuously  and  for  this 
reason  are  steady  in  the  power  required. 

As  far  as  oscillating  motion  goes,  they  are  not  balanced  and 
therefore  give  rise  to  vibration  if  not  on  good  foundation. 

They  are  used  for  the  very  largest  capacity.  The  large 
crusher  (No.  18)  at  the  plant  of  the  Dixie  Portland  Cement 
Company,  near  Chattanooga,  Tenn.,  is  18  ft.  n  in.  in  height  and 
weighs  425,000  pounds.  It  has  a  capacity  of  800  tons  per  hour 


GRINDING  RAW    MATERIAL,   AND    MACHINERY  123 

and  will  crush  pieces  of  rock  3  X  5  X  10  ft.  This  crusher  is, 
however,  unusually  large  for  cement  work  and  is  in  fact  the  larg- 
est ever  built  for  any  purpose.  Gates  crushers  are  well  adapted  for 
free  feeding  or  feeding  directly  from  cars,  and  the  rock  can  be 
fed  into  them  from  all  directions. 

The  smallest  size  crusher  which  finds  a  place  in  a  modern 
cement  mill  is  the  No  6  crusher.  The  newer  mills  employ 
usually  one  large  crusher,  a  No.  9  or  No.  10,  followed  by  two  or 
more  smaller  crushers.  The  No.  9  crusher  is  too  large  to  crush 
stone  fine  enough  for  a  ball  mill  or  a  set  of  rolls  alone  and  should 
always  be  followed  by  a  No.  6  or  other  small  crusher  for  good 
results.  The  No.  7  is  about  the  largest  crusher  which  can  be 
used  alone.  The  product  of  the  large  crusher  should  preferably 
be  spouted  into  the  smaller  ones.  This,  of  course,  necessitates 
setting  this  crusher  high  up  on  massive  concrete  piers.  When 
this  is  undesirable  a  large  bucket  elevator  may  be  employed 
to  take  the  stone  from  this  crusher  to  the  smaller  ones.  In 
some  instances  the  large  crusher  is  located  at  the  quarry  and 
the  small  ones  at  the  mill,  the  rock  being  conveyed  to  the  latter  in 
cars  or  by  belt  conveyors. 

Sometimes  the  product  of  the  big  crusher  is  passed  through 
a  rotary  screen,  in  order  to  separate  from  it  any  fully  crushed 
material  and  allow  only  the  big  pieces  to  go  to  the  small  crusher. 
While  this  relieves  the  small  crushers  of  some  work,  the  screen 
has  to  be  revolved  and  the  extra  elevating  of  the  stone  represents 
a  source  of  trouble  which  more  than  balances  the  gain  at  the 
small  crushers,  so  that  in  general  it  will  be  found  more  satis- 
factory to  pass  all  the  stone  directly  from  the  large  to  the  small 
crushers. 

The  machines  are  massive  and  repairs  generally  require 
handling  large  parts.  On  account  of  the  sidewise  rolling  of  the 
head  upon  the  "concaves"  they  are  less  liable  to  choke  than  the 
ordinary  jaw  crushers. 

The  power  required  to  operate  this  crusher  upon  rocks  of 
moderate  hardness  is  from  I  to  1.2  H.  P.  per  ton  of  rock  crushed 
per  hour,  depending  on  the  fineness  of  the  product. 

Fig.   1 8  shows  a  large  gyratory  installed  in  a  cement  plant. 


124  PORTLAND  CEMENT 

The  Blake  or  jaw  crusher  is  not  now  used  to  any  extent  in 
the  cement  industry  and  hence  need  not  be  described  here. 

Pulverizing  the  Raiv  Material. 

After  passing  through  the  crusher  the  materials  are  pulverized 
by  any  of  the  following  systems : — 

DRY    MATERIALS. 

1.  FuLLER-LEHiGH    MILL. — Preceded   'by    (a)    Ball    mill,    or 
Kominuter  provided  with  perforated  plates  and  without  screens. 
(b)    Set   of   rolls,     (c)    Williams   or  other  hammer  mill,     (d) 
Pot  crusher. 

2.  GRIFFIN  MILL. — Preceded  by  (a)  Ball  mill  or  Kominuter, 
provided  with  perforated  plates  and  without  screens,     (b)    Set 
of  rolls,     (c)  Williams  or  other  hammer  mill,     (d)  Pot  crusher. 

3.  TUBE    MILL. — Preceded   by    (a)    Ball   mill   or   Kominuter, 
fitted  with  screens. 

FOR    WET    MATERIALS 

4.  TUBE  MILL. — Alone  or  preceded  by  an  edge   runner  mill 
(dry  pan,  wet  pan)  for  clay. 

Other  combinations  find  occasional  use  here  and  there  but  the 
above  are  the  approved  ones.  Some  of  the  older  mills  of  the 
Atlas  Portland  Cement  Co.  are  equipped  with  Huntington  mills 
preceded  by  rolls  to  grind  the  cement-rock-limestone  mixture 
which  they  use.  Occasionally  installations  of  three  roll  Griffin 
mills  and  of  Raymond  mills  will  also  be  found  while  at  the 
plant  of  the  Norfolk  Portland  Cement  Co.,  where  a  very  tough 
dry  shell  marl  is  employed,  buhr-stones  are  installed  as  these 
give  a  cutting  action,  which  it  is  claimed  is  best  adapted  to  re- 
ducing this  material  to  a  fine  powder. 

Crushing  Rolls. 

Fig.  19  shows  a  set  of  crushing  rolls,  the  rolls  themselves 
being  only  indicated  by  the  dotted  circles. 

Referring  to  Fig.  19,  which  represents  the  machine  without 
its  dust  covers  and  automatic  feed :  A  represents  the  main 
frame,  having  the  journals  for  the  stationary  rolls  cast  in  one 
piece.  B  is  the  movable  journal  which  is  held  in  the  center  of 


Fig.  18.— Crushers— Tidewater  Portland  Cement  Co.     (One  No.  9  and  two  No.  6 
Allis-Chalmers  crushers.) 


GRINDING  RAW    MATERIAL   AND   MACHINERY 


125 


the  frame,  A,  by  means  of  a  heavy  steel  shaft,  I,  which  passes 
entirely  through  the  frame.  The  swinging  journals  are  held  in 
place  by  the  tension  rods,  C,  to  which  are  attached  nests  of 
powerful  coiled  springs,  D,  held  in  position  by  the  washers  M 
and  K.  The  springs  are  stiff  enough  to  resist  the  pressure  im- 
posed upon  them  by  ordinary  crushing  without  compression,  and 
yield  only  under  abnormal  strains,  due  to  the  accidental  passage 
through  the  rolls  of  foreign  substances,  too  hard  to  crush,  such 
as  broken  drill  points,  etc. 

The  power  is  applied  to  the  rolls  by  means  of  the  pulleys  P. 


Fig.  19.— Set  of  crushing  rolls. 

and  P.  Both  rolls  are  direct  driven.  In  some  forms  of  rolls 
gears  are  used,  and  one  roll  is  driven  from  the  other  by  means  of 
these.  These  gears,  however,  are  liable  to  wear  out  rapidly  from 
the  grit,  etc.,  which  always  finds  its  way  into  them.  Sometimes 
only  one  roll  is  driven.  The  rolls  usually  revolve  at  a  surface 
speed  of  from  600  to  1,000  feet  per  minute. 

Rolls  are  often  supplied  with  automatic  feeds  to  regulate  the 
stream  of  material  passing  through  them.  They  are  also  usually 
enclosed  in  a  dust  proof  casing. 

Pot  Crusher. 
A  form  of  crusher  which  is  often  used  instead  of  rolls  to  re- 


126 


PORTLAND  CEMENT 


duce  the  product  of  the  large  gyratory  crushers  to  material  which 
will  pass  a  one-inch  screen,  is  the  toothed  or  corrugated  spindle 
crusher.  This  is  made  in  a  number  of  forms  and  by  almost  every 
manufacturer  of  crushing  machinery.  The  simplest  form  is  what 
is  commonly  known  as  a  "pot"  crusher  or  "coffee  mill  cracker." 
This  works  on  practically  the  same  principle  as  a  small  hand 
coffee  mill.  It  is  shown  in  Fig.  20.  The  grinding  is  done  be- 


Fig.  20.— Pot  crusher. 

tween  corrugated  surfaces.  The  spindle  revolves  between  fixed 
bearings,  one  in  the  spider  and  one  on  the  base  of  the  mill. 
There  is  no  eccentric  motion,  as  in  a  gyratory  crusher,  and  the 
grinding  is  done  between  the  V-shaped  corrugations  on  the 
spindle  and  hopper  plates.  With  this  form  of  crusher  the  upper 
part  or  hopper  receives  the  material,  which,  as  it  is  reduced,  falls 
to  the  lower  part  of  the  mill,  where  the  grinding  surfaces  have 
a  finer  corrugation  and  are  set  closer  together.  The  mills  are  also 
suitable  for  crushing  soft  shale  and  other  substances  which  choke 
up  the  gyratory  crusher  but  are  not  suited  to  handling  large 
quantities  of  material. 


GRINDING  RAW    MATERIAL  AND   MACHINERY  127 

Hammer  Mill. 

The  hammer  mill  is  made  in  a  number  of  forms,  each  maker 
having  his  own  type  of  mill  and  peculiarity  of  construction.  In 
some,  the  hammers  are  fixed  and  in  some  hinged,  while  in  one 
form  rings  take  the  place  of  hammers.  The  form  shown  in  Fig. 
21  is  the  Williams  mill.  This  is  one  of  the  best  known  of  this 
type  of  granulator-  It  consists  of  a  number  of  hinged  hammers, 
which  revolve  around  a  horizontal  shaft.  These  hammers  crush 
the  material  and  pass  it  out  through  a  grid  screen  as  shown  in 
the  cut.  The  mill  as  now  made  is  provided  with  an  arrangement 


Fig.  2i.— Williams  mill. 

by  which  the  grinding  plates  can  be  moved  nearer  the  hammers, 
by  means  of  a  hand  wheel  on  the  outside,  to  allow  for  the  wear 
of  the  hammers.  In  connection  with  some  form  of  separator, 
this  mill  has  been  used  to  prepare  material  for  the  tube  mill. 

Other  mills  of  this  type  are  the  "Jeffrey  Swing  Hammer  Pul- 
verizer," the  "Pennsylvania  Crusher"  and  the  "Gardener  Mill." 
In  the  latter,  hinged  U-shaped  bars  take  the  place  of  hammers. 

Of  late  years  mills  of  this  type  are  being  tried  to  some  ex- 
tent in  place  of  ball  mills,  particularly  where  these  latter  are 
designed  to  prepare  for  Fuller-Lehigh  or  Griffin  Mills,  as  the 
installation  is  not  only  much  cheaper  of  itself  but  considerable 
building  and  bin  space  is  saved  thereby.  In  spite  of  this,  how- 


128  PORTLAND  CEMENT 

ever,  and  the  fact  that  many  of  the  Western  mills  are  using 
hammer  mills  successfully,  most  of  the  Eastern  mills  have  stuck 
to  the  ball  mills  and  kominuters  for  this  work. 

Large  Williams  Mills  are  now  being  installed  in  several 
plants  to  replace  the  small  crushers  (No.  5)  when  these  latter 
are  used  after  a  larger  crusher.  The  new  "Jumbo"  (No.  6) 
Williams  mill  has  a  capacity  of  from  100-150  tons  of  lime- 
stone per  hour,  reducing  this  from  pieces  2^/2  inches  and  under 
down  to  material  passing  a  %  mch  screen.  Such  material  is 
suitable  without  further  reduction,  to  be  fed  to  the  Fuller-Le- 
high  and  Griffin  Mills,  doing  away  with  ball  mills,  kominuters 
and  rolls. 

Occasionally,  smaller  mills  of  the  swing  hammer  type  are  used 
to  prepare  material  for  the  tube  mill  and  they  are  quite  gener- 
ally employed,  particularly  in  the  West  as  we  have  said,  to  pre- 
pare limestone  and  shale  for  the  Fuller-Lehigh  and  Griffin  Mills. 
They  are  now  considered  very  efficient  for  this  latter  purpose  and 
not  only  cost  less  to  install,  but  give  a  greater  output  per  horse 
power  hour  than  do  either  ball  mills  or  Kominuters.  The  prod- 
uct from  a  No.  3  Williams  Mill  when  used  to  prepare  for 
Giiffin  Mills  ranges  about  as  shown  below. 

Per  cent. 

Passing  No.    2  mesh 100 

"         "       4     "       80 

"       8     "       70 

"     20     "       62 

"     30     "       46 

"        50      "          21 

"     100       "         I9 

The  No.  3  mill  requires  from  40  to  50  horse  power  and  will 
reduce  from  20  to  25  tons  of  material  per  hour  to  ^  inch  and 
under.  The  cost  of  repairs  varies  but  should  not  exceed  Y^ 
cent  per  ton  on  this  class  of  work.  When  preparing  for  a  tube 
mill  the  No.  3  Williams  mill  will  grind  from  8  to  10  tons  per 
hour  to  a  fineness  of  95  per  cent,  passing  the  No.  20  sieve  tak- 
ing pieces  \y2  inches  in  size  with  an  expenditure  of  from  45  to 
55  horse  power  and  a  repair  cost  of  from  i*4  to  2  cents  per  ton 
(=  0.4  to  0.6  cents  per  barrel  of  cement).  The  main  objec- 


GRINDING   RAW    MATERIAL   AND    MACHINERY 


129 


tion  to  this  type  of  mill  is  the  fact  that  if  a  large  piece  of  metal, 
such  as  a  coupling  pin,  finds  its  way  into  it  through  careless- 
ness, the  hammers  are  usually  ripped  off.  The  hammers,  how- 
ever, can  generally  be  replaced  in  a  short  while. 

Edge  Runner  Mill. 

The  edge  runner  (Fig.  22)  is  made  in  two  different  types  and 
under  the  names  "edge  runner  mills,"  "Chaser  mills,"  "Chillean 
Mill,"  "Dry  Pan"  and  "Wet  Pan,"  according  as  used  for  wet  or 


Fig.  22.— Edge  runner  mill. 

dry  grinding.  It  consists  of  a  pan  in  which  revolve  one  or  more 
rollers.  Either  the  pan  itself  or  the  rollers  may  be  driven.  In 
the  first  form,  the  pan  is  driven  and  the  rollers  are  revolved 
by  the  revolution  of  the  former.  In  another  type,  the  pan  re- 
mains stationary  and  the  rolls  are  driven  around.  This  latter 
type  of  mill,  however,  is  much  less  employed  than  the  former 
and  usually  only  in  cases  where  the  nature  of  the  material  would 
allow  slipping  of  the  rollers  as  in  grinding  paints  and  colors  in 
oil.  Both  the  pan  and  runners  are  usually  made  of  cast  iron. 
The  mill  grinds  by  the  weight  of  the  rolls  acting  on  the  particles 
to  be  ground.  Chilled  iron  or  steel  scrapers  or  plows  keep  the 
9 


130 


PORTLAND 


material  to  be  ground  under  the  rolls  as  the  pan  revolves.  Where 
the  material  is  to  be  ground  to  a  definite  size,  the  pan  bottom 
is  often  fitted  with  steel  or  chilled  iron  grids  through  which 
the  fully  ground  material  passes  while  the  unground  is  scraped 
back  under  the  rollers  by  means  of  scrapers. 

The  Ball  Mill. 
The  ball  mill  is  of  European  origin  and  was  used  for  grinding 


Fig.  23.— Ball  mill,  section  showing  grinding  plates  and  sieves. 

Portland   cement  in   Germany  before   its  introduction   into  this 


GRINDING  RAW    MATERIAL  AND   MACHINERY  13! 

country.  It  is  used  in  connection  with  a  pulverizing  mill  to 
prepare  the  material  for  the  latter,  the  ball  mill  reducing  it  to  a 
coarse  grit  and  the  pulverizer  completing  the  operation. 

Figs.  23  and  24  show  the  construction  of  a  ball  mill.     It  con- 


Fig.  24.— Ball  mill,  section  through  the  shaft. 

sists  of  a  drum  containing  a  ton  or  more  of  steel  balls.  The 
drum  is  lined  first  with  steel  or  chilled  iron  plates,  (d)  which 
lap  one  over  the  other  to  form  steps.  As  the  drum  revolves,  the 
balls  drop  over  the  steps  pounding  the  material  to  pieces.  The 


132  PORTLAND  CEMENT 

partially  ground  material  then  drops  through  holes  in  the  plates 
on  to  perforated  steel  screens  (g)  bolted  around  the  entire  cir- 
cumference of  the  drum.  These  screens  retain  the  very  coarse 
particles  and  return  them  to  the  inside  of  the  drum.  The  finer 
ones  drop  on  another  set  of  screens  (/)  made  of  woven  wire  cloth, 
and  these  separate  the  fully  ground  material  from  the  coarse  and 
return  the  latter  back  to  the  mill. 

The  fully  ground  material  falls  into  the  dust  proof  casing, 
which  entirely  surrounds  the  mill,  and  then  down  to  the  conveyor 
running  underneath  the  latter. 

When  the  ball  mill  is  used  to  prepare  material  for  a  Fuller- 
Lehigh  or  a  GrifBn  mill,  no  screens  are  used  and  the  material 
when  reduced  sufficiently,  about  ^  inch  in  diameter  and  under, 
falls  through  the  perforations  in  the  grinding  plates  directly  into 
the  casing.  When  used  in  connection  with  a  tube  mill,  however, 
the  two  sets  of  screens  are  always  necessary. 

The  ends  of  the  drum  are  formed  by  circular  plates.  In  the 
Gates  and  Krupp  forms  of  this  mill  and  also  in  the  smaller  size  of 
the  Smidth  mill  these  plates  have  rigidly  attached  to  their 
centers,  hubs  which  are  mounted  on  to  a  heavy  shaft  which  re- 
volves in  dust  proof  bearings.  One  of  the  hubs  is  provided  with 
openings  through  which  the  material  to  be  ground  is  fed.  In 
the  large  size  Smidth  mills  the  shaft  is  omitted  and  the  hub 
rests  on  roller  bearings  giving  a  full  circular  opening  which  will 
admit  of  the  passage  of  lumps  10  inches  in  diameter  into  the  mill. 
The  feeding  device  of  the  Smidth  mills  consists  of  a  circular  re- 
volving table  provided  with  a  scraper.  The  material  to  be 
ground  is  brought  down  upon  the  table  by  a  spout  which  stops 
short  a  few  inches  from  the  former.  As  the  table  revolves  the 
material  flows  out  of  the  spout  upon  it  and  as  it  comes  around  to 
the  scraper  is  brushed  off  into  the  hopper  of  the  mill.  The  feed 
can  be  regulated  by  adjusting  the  scraper  so  as  to  brush  off  a 
greater  surface  of  the  table.  The  Gates  ball  mill  has  a  swinging 
feeder. 

The  size  of  the  product  of  the  ball  mill  is  regulated  entirely 
by  the  fineness  of  the  finishing  screens.  Those  on  mills  intended 


GRINDING  RAW    MATERIAL   AND    MACHINERY  133 

to  grind  raw  material  are  usually  16  to  18  mesh  and  those  on 
mills  for  clinker  from  18  to  20  mesh.  It  is  generally  economy 
to  so  balance  the  screens  as  to  get  the  most  out  of  the  tube  mill. 
However,  since  the  ball  mill  requires  much  less  power  than  the 
tube  mill  and  consequently  up  to  a  certain  point  should  be  made 
to  do  all  the  work  it  will.  The  screens  of  the  ball  mill  are  apt 
to  leak  occasionally,  both  from  wear  and  also  from  the  dropping 
out  of  a  rivet  or  bolt.  A  good  check  upon  this  is  to  run  sieve  tests 
of  the  product  upon  a  No.  20  sieve  once  or  twice  a  day  and  any 
abnormal  weight  of  residue  should  be  followed  by  an  examina- 
tion of  the  screens  for  leaks.  It  is  necessary  to  brush  the  screens 
off  occasionally  with  a  wire  brush  as  they  clog  with  use. 

All  of  the  interior  parts  of  the  mill  are  of  course  subject  to 
wear.  The  "liners"  or  plates  which  form  the  steps  of  the  mill 
are  usually  made  of  armor-plate,  manganese  steel,  chilled  iron, 
etc.  The  latter  have  only  the  wearing  surface  chilled  and  a 
backing  of  soft  gray  iron  to  prevent  cracking  from  the  impact 
of  the  balls.  The  balls  themselves  are  usually  of  forged  steel 
and  5  inches  in  diameter.  They  gradually  wear  down,  how- 
ever, until  the  charge  in  the  mill  represents  all  sizes  from  5 
inches  down  to  an  inch  in  diameter.  Often  these  small  balls 
are  perfectly  round.  A  set  of  liners  usually  lasts  from  one  to 
two  years  depending  on  their  quality.  When  equipped  with 
fine  screens  (i6-mesh)  and  used  for  granulating  clinker  the 
wear  on  the  balls  amounts  to  about  i  Ib.  per  20  to  30  barrels  of 
cement  ground  or  about  Y^  cent  per  barrel. 

With  all  ball  mills,  a  stack  should  be  connected  to  the  upper 
part  of  the  casing  to  carry  off  the  dust  and  steam.  This  stack 
may  be  carried  out  of  the  building,  but  in  any  event  should  be 
carried  up  high  enough  to  secure  a  good  draft  and  carry  away 
all  of  the  steam  formed  in  the  mill,  by  the  frictional  heat  of  the 
latter  acting  on  the  moisture  in  the  material  ground.  If  the 
steam  is  not  carried  off  the  screens  will  clog  up.  At  one  time 
considerable  attention  was  paid  to  the  dust  also  carried  away, 
in  the  belief  that  it  represented  a  considerable  loss.  At  one 
plant  with  which  the  writer  was  connected,  a  dust  collector  was 
installed  and  an  effort  made,  to  save  the  dust.  This  latter  was 


134  PORTLAND  CEMENT 

found  to  not  only  be  inconsiderable  in  amount  but  also  devoid 
of  cementing  properties  and  proved  upon  analysis  to  be  prac- 
tically fully  hydrated  cement. 

One  objection  to  the  ball  mill  is  the  fact  that  the  screening 
area  is  too  small,  and  efforts  have  been  made  to  get  around 
this  by  modifying  the  mill  in  various  ways.  The  kominuter 
which  is  described  next  is  such  a  modification.  Outside  screens 
have  also  been  tried  but  never  adopted  to  any  extent.  At  the 
plant  of  the  Riverside  Portland  Cement  Co.,  Riverside,  Cal.,  a 
combination  of  ball  mills  and  Newaygo  Separators  is  used,  the 
ball  mills  being  screenless  and  the  separators  located  just  below 
them. 

A  No.  8  ball  mill,  the  size  ball  mill  frequently  installed  in 
cement  plants,  usually  requires  from  40  to  50  horse  power  and 
turns  out  from  4  to  6  tons  of  raw  material  and  from  30  to  40 
barrels  of  clinker  per  hour,  depending  of  course  on  the  fineness 
of  the  screens  when  used  in  connection  with  a  tube  mill.  The 
balls  run  in  sizes  from  3  to  5  inches  in  diameter  and  the  charge 
of  balls  for  a  mill  of  the  above  size  weighs  usually  about  2.^/2 
tons.  As  stated  above,  if  the  ball  mill  is  used  to  prepare  ma- 
terial for  a  Fuller-Lehigh  Mill  or  a  Griffin  Mill,  no  screens  are 
required  and  the  material  passing  through  the  perforations  in 
the  grinding  plates  of  the  ball  mill  is  suitable  for  feeding  to 
these  machines.  This  complete  elimination  of  the  screens,  ma- 
terially increases  the  output  of  the  ball  mill.  For  example, 
whereas  a  No.  8  Krupp  ball  mill  acting  as  a  preliminary  mill  to 
a  tube  mill,  has  a  capacity  of  from  four  to  six  tons  per  hour  at 
an  expenditure  of  about  45  horse  power,  the  same  ball  mill,  act- 
ing as  a  preliminary  machine  to  either  of  the  two  mills  men- 
tioned above,  has  a  capacity  of  from  15  to  20  tons  per  hour  with- 
out in  any  way  increasing  the  power  required  to  operate  the 
machine. 

The  repairs  on  a  ball  mill  are  fairly  heavy,  particularly  where 
new  liners  are  included  in  these.  Generally  they  consist  of 
bolts  which  drop  out  and  screens  which  must  be  replaced  be- 
cause of  wear.  The  repairs,  including  wear  on  balls  and  liners, 
amount  to  about  %  to  1^2  cent  per  barrel  on  clinker  and  about 


Fig.  25.— Allis-Chalmers  ball  mills— Plant  No.  3,  Universal  Portland  Cement  Co. 


Fig.  27.— Smidth  Kominuters— Three  Forks  Portland  Cement  Co.,  Trident,  Mont. 


GRINDING  RAW    MATERIAL   AND   MACHINERY 


135 


YZ  cent  per  barrel  on  raw  material.  When  used  without  screens 
for  preparing  material  for  the  Fuller  and  Griffin  mills  the  cost 
is  only  a  fraction  of  this,  however. 

Fig.  25  gives  an  idea  of  an  installation  of  ball  mills  in  a  mod- 
ern Portland  cement  plant.  As  will  be  seen  the  mills  are  placed 
between  massive  concrete  piers,  and  are  arranged  side  by  side 
so  that  all  may  discharge  into  the  same  screw  conveyor.  The 
stock  boxes,  containing  the  material  to  be  ground,  are  just  above 
the  feed  end  of  the  mill. 

The  Kominuter. 

A  modification  of  the  ball  mill  which  has  been  introduced  in 
the  last  three  years  by  Messrs.  F.  L.  Smidth  &  Co.  is  the 
Kominuter.  This  form  of  mill  is  intended  to  do  the  work  of 
the  ball  mill  and  is  now  installed  by  this  firm  in  place  of  ball  mills. 
It  consists,  Fig.  26,  of  a  drum  of  about  the  same  diameter  as  a 


Fig.  26. — The  Kominuter. 

ball  mill  but  of  about  twice  the  length  of  the  latter,  suspended 
on  a  shaft  supported  by  bearings.  The  kominuter  is  lined  just 
as  a  ball  mill  is  with  wrought  iron  or  steel  grinding  plates  ar- 
ranged to  lap  and  form  steps.  The  drum  is  surrounded  by  a 
coarse  screen  tilting  slightly  towards  the  feed  end,  and  outside 
of  this  screen,  yet  another  one  of  wire  cloth.  The  material 
enters  through  an  opening  beside  the  shaft  and  is  pounded  to 
pieces  by  the  balls.  It  does  not  fall  out  through  the  screens, 


136 


PORTLAND  CEMENT 


however,  at  once,  but  travels  through  the  full  length  of  the 
drum  and  passes  through  openings  at  the  opposite  end,  on  to  the 
first  coarse  screen,  or  perforated  plate.  The  particles  too  large 
to  pass  through  this  are  returned  automatically  to  the  interior 
of  the  mill  by  means  of  buckets  and  S-shaped  pipes.  The  ma- 
terial passing  the  inside  screen  is  caught  upon  the  outside  one  of 
wire  cloth  and  separated  further  here,  the  coarse  material  being 
returned  to  the  mill  as  before.  The  feeding  device  has  been 
described  in  the  preceding  section  and  is  the  same  as  that  em- 
ployed on  the  small  Smidth  ball  mills. 

The  kominuter  has  possibly  a  little  greater  capacity  than  a  No. 
8  ball  mill  and  requires  the  same  horse"  power.  The  writer's 
opinion,  however,  is  that  it  is  more  troublesome  to  repair,  but 
offsetting  this  is  the  fact  that  it  gives  a  finer  product  and  un- 
questionably has  the  best  feeding  device  of  any  mill  of  this 
class.  Fig.  26  shows  an  installation  of  Kominuters  at  the  plant 
of  the  Three  Forks  Portland  Cement  Co.,  Trident,  Mont. 

The  Tube  Mill. 
The  tube  mill,  Fig.  28,  consists  of  a  cylinder,  20  to  22  feet 


Fig.  28.— Smidth  tube  mill. 

long  and  from  60  to  96  inches  in  diameter,  partly  filled  with  flint 
balls.  This  cylinder  is  lined  with  some  hard  substances  such  as 
armor  plate,  chilled  iron,  quartz,  or  trap-rock  and  revolves  at  a 
speed  of  from  25  to  27  revolutions  per  minute.  The  material 
is  fed  in  through  a  hollow  shaft  and  leaves  either  in  the  same 
manner  at  the  opposite  end  or  else  through  a  grating  at  the 
perimeter  of  the  end.  In  the  Smidth  tube  mill  the  latter  course 


GRINDING  RAW    MATERIAL   AND   MACHINERY  137 

is  pursued,  and  in  the  Gates  and  Krupp  mills  the  former  plan  is 
followed.  The  flint  pebbles  are  generally  imported  from  Europe 
and  wear  at  the  rate  of  about  one  pound  to  thirty  barrels  of 
cement.  Steel  balls  are  sometimes  used  in  tube  mills  grinding 
wet  materials.  The  material  is  usually  fed  into  the  tube  mill  by 
means  of  a  screw  conveyor  operated  by  a  step  pulley  which 
permits  the  cutting  down  of  the  feed,  or  by  a  roller  feed  with 
movable  gates,  or  by  a  shaker  feed,  any  of  which  can  be  adjusted 
to  regulate  the  'amount  of  material  going  into  the  mill.  A  tube 
miM>  5^2  X  22  feet,  usually  requires  80  horse  power  to  run  and 
about  double  that  quantity  momentarily  in  starting.  It  should 
turn  out  about  4  to  6  tons  of  raw  material  per  hour  and  from 
14  to  20  barrels  of  cement. 

The  fineness  of  the  product  turned  out  by  the  tube  mill,  de- 
pends entirely  upon  the  feed.  That  is  within  certain  limits,  the 
less  material  fed  into  the  mill  the  finer  the  product.  The  writ- 
er's experience  has  been  that  the  product  of  the  tube  mill  var- 
ies considerably  in  point  of  fineness.  This  is  no  doubt  due  to 
the  fact  that  the  feeders  do  not  supply  the  material  to  the  mill 
in  a  regular  enough  stream  and,  since  the  fineness  of  the  prod- 
uct is  controlled  indirectly  by  the  quantity  of  material  fed  to 
the  mill,  it  follows  that  there  is  considerable  variation  in  fineness 
if  the  feed  is  irregular.  Samples  taken,  say  every  half  hour, 
from  one  tube  mill  will  frequently  show  a  variation  of  10  per 
cent,  between  extremes,  when  tested  on  the  No.  100  sieve,  al- 
though the  feed  may  not  have  been  altered  during  that  time. 
Of  course  where  a  number  of  mills  are  working  side  by  side,  the 
samples  drawn  for  the  combined  product  at  similar  intervals  do 
not  show  such  variations. 

As  showing  the  progress  of  the  grinding  in  a  tube  mill,  Fig. 
29,  will  be  found  interesting.  A  5^  X  22  ft.  tube  mill  was  shut 
down,  the  man-hole  taken  off  and  samples  drawn  every  4  ft. 
from  the  mill.  These  samples  were  tested  for  fineness  and  the 
results  plotted  to  curves  as  shown  in  the  diagram. 

The  tube  mill  is  usually  lined  with  silex  or  trap-rock  blocks 
or  chilled  iron  plates.  The  blocks  are  about  6  X  8  in.  area 
and  3  ins.  thick  and  are  laid  in  with  Portland  cement.  The 


138 


PORTLAND  CEMENT 


chilled  iron  plates  are  usually  bolted  in.  The  lining  has  an 
important  bearing  on  the  output  of  the  mill,  as  unquestionably 
considerable  pulverizing  is  done  between  the  pebbles  and  the 
lining.  Hence,  in  selecting  material  for  the  latter,  it  is  not  only 
necessary  to  secure  a  hard  material  which  will  wear  well,  but 
also  one  which  will  grind  well.  The  writer  has  known  the  ca- 
pacity of  a  tube  mill  lined  with  chilled  iron  plates  to  be  mate- 


307. 


00 


20' 


O' 


/O' 


Fig.  29.— Cement  fineness  determinations  in  a  5  ft.  X  22  ft.  tube  mill. 

rially  increased  by  substituting  for  the  iron  lining  one  of  the 
silex.  This  is  to  be  expected,  for  no  metal  disk  begins  to  ap- 
proach the  grinding  done  by  a  mill  stone,  when  used  similarly 
to  the  latter.  Practically  all  pebbles  used  in  this  country  are 
imported  from  France  and  Denmark,  although  one  or  two  of  the 
Western  mills  have  found  local  pebbles  which  give  them  good 
satisfaction.  Generally,  the  American  product  proves  too  soft 
and  breaks  up  in  the  mill.  A  good  pebble  should  stand  a  con- 
siderable blow  with  a  hammer,  without  breaking,  and,  in  the 


GRINDING  RAW    MATERIAL  AND   MACHINERY 


139 


mill,  should  wear  down  and  not  break  up.  Except  in  starting 
up  a  mill,  no  small  pebbles  are  used  and  those  fed  in  are  oval 
shaped  and  about  3X2  inches.  Crushed  trap-rock  has  been 
tried  a  number  of  times  in  place  of  pebbles,  but  results  obtained 
do  not  seem  to  warrant  general  adoption  of  this  material  at 
any  mill.  The  mill  is  usually  rilled  with  pebbles  to  slightly 
above  the  center  line.  As  those  pebbles  above  the  line  balance 
a  corresponding  weight  of  those  below,  an  extra  weight  of  peb- 
bles is  obtained  without  increasing  the  H.  P.  required  to  turn 
the  mill,  over  the  older  way  of  not  quite  half  filling  the  mill. 
This  extra  load  of  pebbles,  provided  it  is  not  carried  too  far,  ma- 
terially increases  the  output  of  the  mill. 

Efforts  have  been  made  to  substitute  for  a  ball  mill  a  tube 


Fig.  30.— Ball-tube  mill.     (Chalmers  &  Williams  Co.) 

mill  in  which  the  lining  was  made  of  chilled  iron  and  corrugated 
slightly,  the  pebbles  being  replaced  by  steel  balls,  the  idea  being 
to  do  away  with  the  screens  of  the  ball  mill,  always  a  source 
of  trouble.  Such  a  mill  under  the  name  "ball-tube  mill,"  has 
found  a  limited  use  as  a  preparatory  mill  for  the  tube  mill.  This 
latter  type  of  pulverizer,  however,  does  not  pulverize  coarse 
material  very  readily  and  requires  a  very  regular  and  not  too 
coarse  feed,  the  very  large  pieces  usually  working  their  way 
entirely  through  the  mill  without  being  reduced  much  in  size. 
Hence  the  ball-tube  mill  has  not  found  very  general  use.  Fig. 
30  shows  the  ball  tube  mill  made  by  the  Chalmers  &  Williams 


I4O  PORTLAND  CEMENT 

Co.  In  a  German  type  of  mill,  (Lohnert's  Compound  Mill") 
both  ball  and  tube  mills  are  combined  in  one.  The  feed  end  of 
the  cylinder  is  larger  in  diameter  than  the  main  portion  and  is 
provided  with  a  step  lining,  this  compartment  which  contains  the 
steel  balls  being  separated  from  the  rest  of  the  mill  by  means  of 
a  diaphragm.  The  lower  part  of  the  mill  is  filled  with  pebbles. 
The  material  is  first  granulated  in  the  upper  part  and  then  pul- 
verized in  the  lower. 

Recently  the  plan  has  been  tried  at  a  number  of  plants  of 
replacing  about  a  fifth  of  the  pebbles  in  the  tube  mill  with  small 
metal  slugs  known  as  "Cylpebs."  These  slugs  are  about  one 
inch  long  by  about  l/2  inch  in  diameter  and  are  made  of  some 
hard  material  such  as  chilled  iron  or  alloy  steel.  The  tube  mill 
is  provided  with  a  perforated  diaphragm  about  4  feet  from  the 
discharge  end  and  the  compartment  so  formed  is  filled  half  full 
of  the  "cylpebs."  This  end  of  the  mill  is  lined  with  chilled  iron 
plates. 

The  addition  of  the  "cylpebs"  increases  the  output  of  the  mill 
at  least  33^3  per  cent,  but  of  course  also  increases  the  power 
required  to  operate  the  mill.  The  writer  is  informed  by  a 
user  that  this  is  about  25  per  cent.  The  addition  of  the  "cylpebs" 
therefore  increases  the  output  per  H.  P.  hour  also.  Since 
"cylpebs"  are  more  expensive  than  pebbles,  part  of  this  gain 
is  offset  by  increased  cost  of  maintenance  of  the  tube  mill.  They 
not  only  increase  the  output  but  also  increase  the  finer  parti- 
cles in  cement.  That  is  to  say,  in  two  samples  of  cement,  one 
ground  in  a  mill  equipped  with  cylpeb  and  the  other  in  one 
without,  the  cylpeb  ground  cement  will  be  found  to  test  the 
finer  on  the  No.  200  sieve.  This  is  shown  by  the  results  given  on 
page  141.  The  results  show  the  fineness  obtained  without  "cylpebs" 
and  with  them,  at  the  same  mill. 

The  tube  mill  is  driven  by  means  of  a  girth  and  a  spur  gear. 
This  should  run  so  that,  on  the  side  at  which  the  spur  meshes 
with  the  tube  mill  gear,  the  teeth  are  moving  upward.  This  is 
done  for  two  reasons — first  so  that  tools,  clinker,  etc.,  which 
fall  into  the  gearing  will  be  thrown  away  from  the  teeth  and  not 
drawn  in  between  them,  resulting  in  stripped  gears  and  broken 


GRINDING  RAW    MATERIAL  AND   MACHINERY  141 

COMPARISON  OF  CEMENT  GROUND  WITH  AND  WITHOUT  "CYLPEBS." 


Passing  No.  TOO  sieve. 

Passing  No.  200  sieve. 

With  

Q2  Q 

80  7 

Q2.Q 

•JA    T 

With 

y*'y 

r\A    A 

Sy   f\ 

V4-4 
QA  A. 

76  A. 

With   

QC    8 

86  3 

Without    

06  o 

7Q  ^ 

With   

Q7  O 

/y-o 
87  8 

Without               

lr/«w 

Q7  O 

81  Q 

y/.u 

01.  y 

teeth;  second  when  running  in  this  direction  the  pressure  is 
against  the  base  and  not  the  cap  of  the  bearing.  Owing  to  their 
length,  a  battery  of  tube  mills  is  a  difficult  proposition  to  drive 
directly  from  one  line  shaft  and  considerable  power  is  often 
wasted  in  counter  shafts.  The  employment  of  a  bevel  gear 
helps  simplify  the  arrangement  as  it  allows  the  mills  to  be 
placed  side  by  side  and  the  line  shaft  to  be  run  at  right  angles 
to  the  mills.  The  bevel  gears,  however,  'are  unsatisfactory 
and  in  spite  of  the  simplifying  of  the  arrangement  of  the  mills, 
are  but  little  employed.  Motor  drives  allow  an  ideal  arrange- 
ment of  the  mills,  side  by  side,  which  cannot  be  done  without 
countershafting  where  more  than  two  or  three  mills  are  driven 
from  the  same  line  shaft. 

A  new  form  of  drive  used  in  place  of  the  gears  is  the  Lenix 
drive.  With  this  drive  a  tire  of  large  diameter  is  fastened  to 
the  tube  mill  by  means  of  iron  rods  or  posts.  A  belt  is  passed 
around  this  and  the  small  pulley  on  the  driving  shaft.  The  belt 
is  made  to  wrap  around  nearly  three-quarters  of  the  surface 
of  the  latter  by  means  of  an  idler,  instead  of  gripping  only  a 
small  portion  of  its  rim,  as  would  be  the  case  with  an  ordinary 
belt  drive  between  such  short  centers. 

Fig.  31  shows  a  tube  mill  installation  in  one  of  the  newest 
Portland  cement  plants. 


142 


PORTLAND 


Fuller-Lehigh  Mill. 

The  Fuller-Lehigh  Mill  (Lehigh  Car,  Wheel  &  Axle  Works, 
Catasauqua,  Pa.,  see  Fig.  32),  has  for  its  grinding  element  a  hori- 
zontal ring  or  die,  A,  against  which  revolve  four  balls,  B,  12 
inches  in  diameter.  These  balls  are  propelled  by  four  equidistant 


Fig.  32.— Fuller-Lehigh  pulverizer.     (Lehigh  Car,  Wheel  and  Axle  Works.) 

pushers,  C,  radiating  from  a  vertical  central  shaft.  The  balls 
revolve  at  a  speed  of  160  R.  P.  M.  and  hence  press  against  the 
material  on  the  die  with  enormous  (centrifugal)  force. 

The  material  to  be  reduced  is  fed  to  the  mill  from  an  overhead 
bin  by  means  of  a  feeder  mounted  on  top  of  the  mill.  This  feeder 
is  driven  direct  from  the  mill  shaft  by  means  of  a  belt  running 
over  a  pair  of  three  step  cones,  which  permits  the  operator  to 
accomodate  the  amount  of  material  entering  the  mill  to  the  nature 
of  the  material  being  pulverized.  In  addition  the  feed  hopper  is 


GRINDING  RAW    MATERIAL  AND   MACHINERY  143 

provided  with  a  slide  so  that  the  rate  of  flow  of  material  from  the 
bin  to  the  feeder  can  be  controlled. 

After  the  material  is  discharged  by  the  feeder,  it  falls  to  the  die 
where  it  is  reduced  to  a  fine  powder  by  the  rolling  action  of  the 
balls  against  the  material  in  the  die,  the  grinding  action  being 
similar  in  all  respects  to  a  mortar  and  pestle  action. 

Above  the  die  and  the  balls  there  is  a  fan  which  is  attached 
to  the  yoke  propelling  the  balls.  This  fan  has  two  rows  of  fan 
blades,  one  above  the  other.  The  lower  set  of  fan  blades  lifts  the 
finely  pulverized  material  from  the  pulverizing  zone  into  a  cham- 
ber above  the  die,  where  it  is  held  in  suspension  until  it  is  floated 
out  through  a  screen  which  completely  encircles  this  chamber  by 
means  of  the  fanning  action  of  the  upper  row  of  fan  blades. 

The  mill  is  provided  with  two  screens;  one,  the  inner,  R,  of 
about  one  inch  mesh,  is  made  of*  perforated  sheet  steel  and  pro- 
tects the  outer  screen,  N.  The  outer  or  finishing  screen  does 
not  really  screen,  but  merely  serves  to  control  the  draft  of  air 
generated  by  the  fan,  and  hence  the  fineness,  since  the  greater  the 
velocity,  the  greater  the  carrying  power  of  the  air,  and  hence  the 
coarser  the  product. 

When  the  mill  is  in  operation,  it  is  continually  handling  only 
a  limited  amount  of  material  at  any  one  time.  As  soon  as  the 
material  is  reduced  to  the  desired  fineness,  it  is  lifted  out  of  the 
pulverizing  zone  and  discharged  from  the  machine.  The  power 
required  to  operate  the  machine  is  applied  directly  to  either 
crushing  the  material  or  consumed  in  friction  between  the  push- 
ers and  balls  and  the  shaft  and  bearings. 

The  fineness  is  controlled  to  some  extent  by  the  size  screens 
employed,  and  also  by  the  amount  of  material  fed  to  the  mill, 
as  explained  above.  Provided  the  screens  are  kept  free  from 
holes,  these  mills  give  a  very  regular  fineness.  A  peculiarity 
of  the  product  of  the  Fuller  Mill  is  the  fact  that  the  percentage 
of  material  passing  a  No.  200  sieve  which  it  contains  is,  relative 
to  the  No.  100  sieve,  very  high.  This  is  due  to  the  great  crush- 
ing force  applied  to  such  a  small  quantity  of  material  as  lies 


144  PORTLAND 

between  the  ball  and  the  die  and  also  to  some  extent  to  the 
rubbing  action  between  the  ball  and  the  die. 

The  Fuller  mill  is  usually  driven  from  either  a  line  shaft  or  a 
motor  by  means  of  a  quarter  turn  belt.  If  from  a  line  shaft, 
a  clutch  is  employed  on  the  latter,  so  that  the  mill  may  be  cut 
off  for  repairs  at  any  time.  Recently  vertical  motors  have  been 
found  a  very  efficient  means  of  driving  the  mill,  as  they  do 
away  with  the  quarter  turn  belt,  and  a  number  of  the  newer 
installations  of  this  pulverizer  follow  this  plan.  Fig.  33  shows 
a  battery  of  Fuller  Mills  so  driven. 

The  first  Fuller-Lehigh  mill  brought  out  had  a  36-inch  die, 
but  the  size  now  generally  employed  in  the  cement  industry  has 
a  42  inch  die.  A  mill  of  this  latter  size  will  pulverize  5  to  7 
tons  of  raw  material  per  hour  with  an  expenditure  of  65  to  75 
horse  power  or  from  10  to  15  barrels  of  clinker  with  70  to  85 
horse  power. 

The  manufacturers  of  the  Fuller  mill  have  recently  brought 
out  a  much  larger  mill  with  a  54  inch  die  under  the  name  of  the 
"Fuller-Dreadnaught."  One  of  these  mills  is  now  employed  at 
the  plant  of  the  Allentown  Portland  Cement  Co.,  on  clinker 
where  it  is  claimed  that  the  output  is  25  barrels  per  hour  and 
100  to  125  horse  power  are  required  to  run  the  mill. 

The  Fuller  mill  requires  careful  attention,  but  when  handled 
properly  gives,  relatively  speaking,  a  high  output  for  the  power 
it  requires.  The  principal  wearing  parts  are  the  pushers  and 
balls.  When  the  latter  w^ar  flat  the  mill  requires  more  power 
and  gives  less  output.  The  die  also  is  subject  to  some  wear 
and  the  outer  or  fine  screens  are  liable  to  both  tear  and  wear. 
The  cost  of  repairs  on  raw  materials  amount  to  from  1.3  to  2 
cents  per  ton  (=  0.4  to  0.6  cents  per  barrel  of  cement)  and  on 
clinker  from  y$  to  il/2  cents  per  barrel. 

The  mill  takes  up  but  little  floor  space  and  does  not  require 
very  massive  foundations.  Usually  they  are  set  up  with  about 
Sy2  ft.  between  centers  and  a  platform  is  placed  beside  and 
around  the  mill  just  below  the  die,  as  will  be  seen  by  referring 
to  Fig.  33. 


31-— Allis  Chalmers  tube  mills— Plant  No.  3,  Universal  Portland  Cement  Co. 


Fig.  33- — Fuller-Lehigh  pulverizers  with  motors— Raw  mill  of  the  Tidewater 
Portland  Cement  Co.,  Union  Bridge,  Md. 


GRINDING  RAW    MATERIAL   AND   MACHINERY 


Griffin  Mill. 

The  Griffin  Mill   (Bradley  Pulverizer  Co.,  Boston,  Mass.)   is 
shown  in  Fig.  34.     Referring  to  this  it  will  be  seen  that  it  con- 


$$, 

mm 


-  34-—  Griffin  mill.     (Bradley  Pulverizing  Co.) 


sists  of  a  steel  die  or  ring,  e,  against  which  a  roll,  c,  also  of  steel 
is  made  to  revolve,  and  it  is  between  the  face  of  these  two  that  the 
material  is  ground.  The  roll  is  suspended  by  a  shaft,  a,  from  a 
spider,  d,  and  is  actuated  by  a  pulley,  £,  to  which  the  shaft  is 

10 


146  PORTLAND  CEMENT 

attached  by  universal  joint,  /.  The  fully  ground  material  is  sucked 
up  and  forced  through  screens,  b,  by  fans,  g,  attached  to  the 
shaft  and  the  coarse  particles  falling  back  into  the  pan,  d,  of  the 
mill  are  drawn  between  the  fan  and  the  die  by  means  of  plows,  k, 
attached  to  and  below  the  roll.  The  finished  product  passes 
through  the  screens  and  downward  between  these  and  the  outer 
casing,  through  openings  in  the  base  to  the  screw  conveyor, 
i,  located  below  the  mill. 

The  roll  is  revolved  within  the  die  in  the  same  direction  that 
the  shaft  is  driven,  but  when  coming  in  contact  with  the  die  it 
travels  around  the  die  in  the  opposite  direction  from  that  in  which 
the  roll  is  revolving  with  the  shaft.  The  roll  is  pressed  out 
against  the  die  by  centrifugal  force,  the  amount  of  this,  of  course, 
depending  on  the  weight  of  the  roll  and  the  speed  at  which  the 
shaft  revolves.  This  mill  is  made  in  three  sizes : — viz,  with  30, 
36  and  40  inch  dies.  Formerly  the  30  inch  mill  was  used  in  the 
cement  industry.  Recently  the  40  inch  mill  has  been  introduced. 

The  fineness  is  controlled  by  the  size  screen  employed,  which 
serves  to  regulate  the  draft  and  is  not  intended  to  screen,  and 
also  by  the  amount  of  material  fed  to  the  mill. 

The  Griffin  mill  like  the  Fuller-Lehigh,  takes  up  small  floor 
space  and  may  be  driven  by  any  of  the  methods  mentioned  for 
transmitting  power  to  the  Fuller-Lehigh  mill.  The  saving  in 
the  cost  of  buildings  effected  by  an  installation  of  either  Griffin 
Mills  or  Fuller-Lehigh  Mills  over  one  of  ball  and  tube  mills  is 
considerable  and  it  is  claimed  that  with  a  3,000  barrel  per  day 
mill  this  saving  would  amount  to  $20,000. 

The  product  of  the  Griffin  mill  is  fairly  constant  as  regards 
fineness,  though  as  with  all  mills  of  this  class  the  screens  must 
be  carefully  watched,  as  when  a  tear  occurs  in  them  much 
coarse  material  leaks  through.  The  product  of  the  40  inch 
Griffin  mill  contains  for  the  same  fineness  on  the  No.  100  sieve 
more  material  passing  the  200  sieve  than  does  the  30  inch  Griffin. 

The  sieves  employed  are  usually  24  to  28  mesh  for  grinding 
raw  material  to  a  fineness  of  92  per  cent,  through  the  No.  100 
sieve  and  30  or  32  mesh  for  grinding  clinker  to  the  same  fine- 
ness. 


GRINDING  RAW    MATERIAL  AND   MACHINERY  147 

The  material  to  be  pulverized  should  be  fed  to  the  Griffin  mill 
crushed  to  y2  inch  size  and  under.  The  speed  of  the  driving 
pulley  on  the  30  inch  mill  is  between  190  and  200  R.  P.  M.  and 
the  weight  of  the  roll  100  Ibs. 

The  principal  parts  subject  to  wear  are  the  die  and  roll.  The 
shafts  also  frequently  break  and  the  screens  as  we  have  said 
get  torn.  Repairs  on  raw  material  generally  run  from  1.6  to 
2.6  cents  per  ton  (=0.5  to  0.8  cents  per  barrel  of  cement  pro- 
duced) and  on  clinker  from  iy2  to  2l/2  cents  per  barrel.  Both 
manganese  steel  and  chilled  iron  rolls  and  dies  are  employed. 
The  breaking  of  the  shafts  constitutes  an  item  in  the  cost  of 
keeping  these  mills  in  repair.  The  idea  of  the  wooden  frame 
is  to  lessen  the  shock  on  the  shaft  and  so  decrease  the  breaks. 
The  40  inch  mill  has  a  frame  built  up  of  angle  irons,  for  the 
same  reason,  as  such  a  frame  is  more  elastic  than  one  made  of 
cast  iron.  The  die  usually  wears  most  at  the  center  and  be- 
comes concave,  when  this  occurs  the  upper  and  lower  edges  of 
the  roll  are  liable  to  come  in  contact  with  the  bare  metal  of  the 
die,  causing  portions  of  the  roll  to  be  broken  off.  This  is 
avoided  in  some  plants  by  removing  the  dies  when  they  become 
worn  and  turning  them  even  on  a  lathe.  The  parts  to  the  mill 
are  light  and  it  can  easily  be  taken  apart  and  repaired. 

A  30  inch  Griffin  mill  requires  about  25  to  30  H.  P.  and  gives 
an  output  of  from  \y2  to  2  tons  of  raw  material  when  grind- 
ing to  a  fineness  of  92  per  cent,  through  the  No.  100  sieve  and 
4  to  6  barrels  of  clinker  with  an  expenditure  of  from  30  to  35 
H.  P.  grinding  to  the  same  degree  of  fineness.  The  40  inch 
G.  iffin  mill  will  grind  about  100  per  cent,  more  than  the  30  inch 
mill  and  require  fro-n  f^  tr.  P.  when  working  on  soft  raw 
materials  to  70  H.  P.  on  clinker. 

About  five  years  ago,  the  manufacturers  of  the  Griffin  mill 
brought  out  a  three  roll  mill  somewhat  similar  to  the  single 
roll  Griffin  mill  just  described,  and  also  to  the  Huntington  mill 
mentioned  below.  This  mill  has  three  rolls,  in  place  of  the 
one  roll  of  the  older  form,  which  are  suspended  by  suitable 
means  from  a  single  shaft,  to  which  latter  is  keyed  the  driving 
pulley.  The  mill  is  provided  with  screens,  fans  and  ploughs 


148 


PORTLAND  CEMKNT 


which  perform  the  same  work  as  in  the  single  roll  Griffin  mill. 
These  mills  were  given  quite  a  trial  in  the  industry  just  after 
their  introduction,  but  in  general  it  may  be  said  that  they  proved 
somewhat  of  a  disappointment.  They  are  now  used  at  a  few 
plants  to  prepare  for  tube  mills  as  they  do  not  grind  very  finely 
themselves. 

Huntington  Mill. 

The  Huntington  mill  is  another  mill  of  the  impact  or  per- 
cussion type  and  is  somewhat  similar  to  the  former  in  construc- 
tion. So  far  as  the  writer  knows  it  is  used  only  by  the  Atlas 
Portland  Cement  Co.,  Northampton,  Pa. 

The  Huntington  mill,  Fig.  35,  has  shells  freely  suspended  on 


Fig.  36.— Huntington  mill. 

spindles   from   a   revolving   spider.     The   revolution   causes   the 
shells  to  swing  put  and  crush  against  the  edge  of  the  die  ring. 

The  Huntington  mill  is  provided  with  fans  and  screens  and 
there  are  four  shells  or  rolls.  The  machine  generally  is  a  great 
consumer  of  repairs  and  does  not  give  a  very  fine  product,  so 


Fig.  35-— The  Giant  Griffin  mill  (side  view) 


Fig.  37-— Raymond  mills— Raw  department  of  the  Crescent  Portland 
Cement  Co.,  Wampum,  Pa. 


GRINDING  RAW    MATERIAL   AND   MACHINERY  149 

that  it  is  now  generally  used  only  to  prepare  material  for  tube 
mills. 

When  so  used,  the  Huntington  mill  will  granulate  from  12  to 
1 8  barrels  of  clinker  per  hour.  With  an  expenditure  of  70-80 
H.  P.  All  of  the  product  will  pass  a  No.  20  sieve.  On  raw 
material  the  mill  has  a  capacity  of  from  6  to  7  tons  per  hour  and 
requires  55  to  65  H.  P.  when  furnishing  a  product  all  of  which 
will  pass  the  No.  20  sieve. 

Raymond  Roller  Mill. 

The  Raymond  roller  mill  is  shown  in  Fig.  37.  The  pulverizing 
unit  of  this  is  somewhat  similar  to  that  of  the  Huntington  mill. 
There  are  four  rolls  which  swing  outward  by  centrifugal  force 
against  a  ring  die.  A  plow  is  located  ahead  of  each  roll  which 
throws  a  stream  of  material  between  the  face  of  the  roll  and  the 
ring  or  die.  The  air  enters  the  mill  through  a  series  of  openings 
located  around  the  pulverizer  chamber  and  directly  under  the  die 
and  rollers.  The  material  which  has  been  reduced  to  the  required 
degree  of  fineness  is  carried  away  by  air  currents  into  a  separator 
which  is  located  to  the  side  of  the  mill.  This  separator  consists 
merely  of  a  large  cone-shaped  chamber  in  which  the  velocity  of 
the  air,  of  course,  decreases  and  consequently  the  particles  fall 
from  suspension.  The  air  currents  in  this  mill  are  induced  by  a 
blower  which  is  entirely  separate  from  the  mill.  The  size  separa- 
tor employed  depends  to  some  extent  upon  the  fineness  to  which 
the  material  is  to  be  ground. 

The  most  extensive  installation  of  Raymond  mills  is  prob- 
ably that  at  the  new  plant  of  the  Crescent  Portland  Cement  Co., 
Wampum,  Pa.,  (see  Fig.  37)  where  three  of  these  mills  are 
employed  for  grinding  the  coal  and  ten  for  the  raw  materials, 
limestone  and  shale.  The  latter  are  prepared  for  the  Raymond 
mills  by  means  of  Williams  mills,  which  reduce  the  materials 
to  such  a  degree  that  70  per  cent,  of  the  feed  to  the  Raymond 
mills  will  pass  a  No.  20  sieve.  The  capacity  of  the  Raymond 
mills  here  is  given  at  5^  tons  per  hour  when  grinding  to  a  fine- 
ness of  96  per  cent,  passing  the  No.  100  sieve. 

The  mills  like  most  pulverizers  of  the  impact  type  relatively 


150 


PORTLAND  CEMKNT 


speaking,  cost  considerable  to  keep  in  repairs  but  are  economi- 
cal of  power  and  give  a  product  which  is  very  regular  with 
respect  to  fineness. 

Kent  and  Maxecon  Mills. 

These  are  mills  which  have  so  far  been  used  in  connection 
with  some  form  of  separator,  both  to  prepare  material  for  the 
tube  mill  and  also  to  do  the  final  grinding.  They  are  both 
manufactured  by  the  same  firm  and  the  Maxecon  is  an  improved 
form  of  the  older  Kent  mill.  The  principle  of  this  type  of  mill 
is  illustrated  in  Fig.  38  and  consists  of  a  vertical  revolving 


ADJUSTI 
SCREW 


ANY  GROUND    OR    FLOOR 


Fig.  38.— Kent  mill. 

ring,  having  three  grinding  rolls  which  are  mounted  on  horizontal 
shafts  and  which  press  against  the  inner  surface  of  the  ring. 
The  material  to  be  ground  is  fed  on  the  inner  surface  of  the  ring 
and  is  ground  between  this  and  the  rolls.  The  inner  surface 
of  the  ring  is  slightly  concave  and  the  cement  is  kept  in  the 
center  of  this  and  between  the  ring  and  rolls  by  centrifugal 
force. 

These  two  mills  require  the  use  of  an  outside  separator;  that 
is,  the  material  as  delivered  by  the  mills  themselves  consists  of 
both  coarse  and  fine  particles,  and  the  latter  must  be  separated 
from  the  mixture,  and  the  former  returned  to  the  mills  for  fur- 


Fig'  39.' — Maxecon  mills — Plant  of  the  Altoona  Portland  Cement  Co.,  Altoona,  Kansas. 


Fig.  40. — Sturtevant  ring  roll  mill. 


GRINDING  RAW    MATERIAL   AND   MACHINERY  15! 

ther  grinding.  At  the  plant  of  the  Newaygo  Portland  Cement 
Co.,  where  the  Kent  mill  was  used,  the  Newaygo  screen,  de- 
scribed below,  was  devised  for  this  purpose,  but  some  plants 
employing  the  Kent  mill  are  using  air  separators,  which  make 
use  of  a  current  of  air  to  separate  the  fine  fromi  the  coarse 
particles. 

Fig.  39  shows  a  battery  of  Maxecon  mills  at  the  plant  of  the 
Altoona  Portland  Cement  Co.,  Altoona,  Kans.,  where  they  are 
used  in  connection  with  Emerick  separators. 

The  Sturtevant  Ring-Ball  Mill 

The  Sturtevant  ring-roll  pulverizer  is  somewhat  similar  to 
the  Kent  mill  in  principle,  in  that  the  grinding  surfaces  are  in 
the  vertical  plane  and  consist  of  a  ring  and  rolls.  In  the 
Sturtevant  mill,  however,  the  ring  is  fastened  to  a  spider  con- 
nected by  a  shaft  and  is  driven  by  this  and  the  front  of  the  mill 
is  hinged  so  that  easy  access  to  the  interior  may  be  had  for 
repairs.  (See  Fig.  40.) 

Newaygo  Separator. 

The  Newaygo  separator  consists  of  an  inclined  screen  mounted 
at  an  angle  of  about  45°.  The  separating  device  consists  of  two 
sets  of  screens  made  of  wire  cloth,  enclosed  in  a  casing  of  steel 
plates.  One  of  these  screens  is  of  coarse  mesh  and  serves  as  a 
scalper  to  take  off  the  large  pieces  and  one  screen  is  of  fine  mesh 
which  acts  as  the  final  separator.  The  fineness  is  regulated  by 
che  mesh  of  this  screen,  although  the  product  is  always  much 
finer  than  the  screen.  For  instance  a  60  mesh  screen  is  used 
for  a  loo  mesh  product.  On  this  fine  mesh  screen,  are  mounted 
steel  bands  running  from  top  to  bottom.  Similar  bands  are  also 
mounted  on  the  coarse  screen.  Short  steel  bars  pass  through 
the  upper  casing  and  also  through  the  bands  of  the  coarse  screen 
and  rest  upon  the  bands  on  the  fine  screen.  A  shaft  actuated 
by  power  runs  across  the  top  of  the  screen,  outside  the  casing, 
and  on  this  shaft  are  hinged  short  pieces  of  iron  to  form  ham- 
mers. When  the  shaft  turns,  these  hammers  strike  the  short 
steel  bars  resting  on  the  fine  screen  and  the  jar  serves  to  bounce 


152 


PORTLAND  CEMENT 


the  fine  material  through  and  keep  the  screen  from  clogging. 
The  material  to  be  separated  is  fed  on  to  the  top  of  the  screen  by 
means  of  a  screw  conveyor  which  can  be  adjusted  so  as  to  feed 
this  uniformly  all  along  the  width  of  the  screen.  The  coarse 
material  of  course  rolls  over  the  two  screens  and  is  carried  away 
by  a  screw  conveyor  at  the  bottom,  while  the  fine  drops  through 


Fig.  41. — Newaygo  separator. 

and  slides  down  the  casing  in  which  the  screens  are  enclosed  and 
is  carried  away  also  by  a  screw  conveyor.  Fig.  41  illustrates 
the  construction  of  the  Newaygo  separator. 

Air  Separators. 

The  Pfeiffer  separator  is  much  used  in  Germany  and  Europe 
to  take  out  the  fine  material  from  the  product  of  the  ball  mill, 


GRINDING   RAW    MATERIAL   AND    MACHINERY 


153 


and  so  relieve  the  tube  mill  of  some  of  its  work.  The  separator 
is  shown  (in  Section)  in  Fig.  42.  It  consists  of  an  outer  and  an 
inner  cone  of  sheet  metal  as  shown  in  the  drawing.  The 
material  to  be  separated  is  fed  into  the  mill  through  the  hopper 
on  to  a  plate,  which  is  connected  to  a  vertical  shaft,  and  is  re- 
volved at  a  speed  of  about  200  revolutions  per  minute.  The 
material  is  thrown  off  this  plate  in  a  thin  spray,  by  centrifugal 
force,  and  is  met  by  a  current  of  air,  going  in  the  direction  shown 


""-"    Flour 

Fig.  42. — PfeifFer  air  separator. 

by  the  arrows.  The  coarse  particles  fall  through  this  current 
into  the  inner  case,  and  the  finer  one  are  carried  into  the  outer 
space,  between  the  inner  and  outer  cones.  The  air  currents 
are  maintained  by  the  fans  as  shown. 

The  Emerick  separator  is  similar  in  principle  to  the  Pfeiffer 
separator,  but  differs  from  it  somewhat  in  details  of  construc- 
tion. 

Air  separators,  of  both  Pfeiffer  and  Emerick  make  were  given 
quite  an  extensive  trial  in  this  country  some  years  ago,  both 
placed  after  the  tube  mill,  and  also  after  the  ball  mill.  In 


154  PORTLAND  CEMENT 

the  former  case,  the  grit  passed  directly  from  the  ball  mills 
through  the  tube  mills  and  from  the  latter  to  the  separators.  The 
fine  material  is  sent  from  the  separators  to  the  stock  house,  and 
the  coarse  particles  are  returned  to  the  tube  mill. 

At  the  time  the  first  edition  of  this  book  was  published, 
American  cement  manufacturers  generally  were  giving  the  air 
separator  a  trial,  in  most  cases  installing  the  Emerick  separator 
after  the  tube  mill.  At  that  time,  some  very  good  reports  as  to 
efficiency  of  the  combination  were  given  out  both  by  the  separator 
makers  and  certain  cement  manufacturers.  In  general,  how- 
ever, it  may  be  said  that  air  separators  did  not  prove  entirely 
satisfactory.  While  some  few  mills  still  use  them,  the  majority 
of  those  who  tried  them  have  now  given  them  up.  They  have 
been  used  to  some  extent  in  connection  with  the  Kent  mill, 
where  as  we  have  said,  the  need  of  an  outside  screen  has  made 
something  of  this  sort  necessary.  Here  they  seem  to  have  given 
as  good  satisfaction  as  the  screen. 

In  Germany  the  Pfeiffers  are  installing  separators  at  a  num- 
ber of  works  in  connection  with  a  short  tube  mill  filled  with 
steel  balls.  The  product  from  the  latter  is  fed  to  the  separator 
which  takes  out  the  fine  material  and  returns  the  coarse  to  the 
mill  for  further  grinding.  The  separators  are  also  used  to 
reject  the  coarse '  material  and  give  a  very  fine  product. 

As  has  been  said  the  use  of  separators  to  take  out  the  fine  par- 
ticles from  the  ball  mill  product  and  so  relieve  the  tube  mill  of 
part  of  its  work  is  quite  general  in  Germany,  but  so  far  has  not 
been  tried  to  any  extent  in  this  country.  A  ball  mill  provided 
with  i6-mesh  screens  of  No.  3  wire  will  give  a  product  con- 
taining between  15  and  20  per  cent,  of  material  passing  a  'No. 
200  test  screen.  The  Kominuter  on  the  other  hand  gives  a  much 
larger  percentage  of  fine  material,  as  would  be  supposed  since 
the  material  must  travel  from  end  to  end  of  the  drum  before 
passing  out,  while  in  the  ball  mill  it  falls  through  the  plates  and 
screens  as  soon  as  ground.  A  test  of  the  Kominuter  product 
made  by  the  writer  gave  25  per  cent,  passing  through  a  No.  200 
sieve  and  40  per  cent,  through  a  No.  100  sieve.  In  this  case  the 
screens  were  16  mesh  and  of  No.  23  wire.  A  finer  mesh  screen 


GRINDING  RAW    MATERIAL  AND   MACHINERY  155 

on  either  ball  mill  or  Kominuter  will,  of  course,  give  a  product 
containing  more  fine  material.  This  fine  material  from  the  Komi- 
nuter contains  considerable  flour  as  sand  briquettes  made  of  the 
material  passing  a  No.  200  sieve  gave  335  Ibs.  for  7  days  and  447 
Ibs.  for  28  days.  The  material  passing  the  No.  100  sieve  gave  267 
Ibs.  for  7  days  and  320  Ibs.  for  28  days. 

A  rather  amusing  discussion1  of  the  separator  question  appear- 
ed in  one  of  the  engineering  magazines,  some  years  ago,  in 
which  the  writer  took  the  ground  that  the  separators  destroy  the 
uniformity  of  the  product  and  that,  for  example  in  a  clay-lime- 
stone mixture,  the  lighter  particles  of  clay  would  be  blown  away 
from  the  heavier  limestone.  The  author  seems  to  have  overlooked 
the  fact  that  by  pulverizing  the  limestone  particles  a  little  finer 
they  too  will  be  blown  out  by  fans  of  the  separator  so  that  while 
it  may  be  true  that  on  starting  up  a  new  separator  the  first 
product  will  be  slightly  over-clayed,  the  trouble  will  be  adjusted 
by  the  return  of  the  limestone  to  the  grinder  for  finer  pulveriz- 
ing, after  which  it  will  be  blown  out  on  its  next  passage  through 
the  separator  together  with  the  clay  from  the  new  lot  of  mix 
fed  into  the  tube  mill,  the  process  being  a  continuous  one.  This 
same  objection  can  be  raised  against  ball  mills,  that  the  softer 
particles  of  clay  or  cement-rock  will  be  pulverized  sooner  and 
drop  through  the  screens  of  the  ball  mill  before  the  limestone. 
In  this  case  also  this  irregularity  adjusts  itself  and  in  the  same 
manner.  My  own  personal  experience  with  air  separation  at 
the  plant  of  the  Edison  Portland  Cement  Co.  convinces  me  that 
there  is  nothing  against  its  use  on  the  ground  of  lack  of  uni- 
formity in  the  product.  In  both  the  Fuller-Lehigh  and  Griffin 
mills  the  separation  of  the  finer  from  the  coarser  particles  is 
effected  by  air  separation,  as  fans  are  used  in  these  mills  to 
blow  the  fine  material  through  the  screen. 

Capacity  of  Various  Grinders. 

Below  will  be  found  a  table  (XIII)  giving  the  capacity  of 
the  various  machines  used  for  crushing  and  grinding  the  raw 

1  "  Some  of  the  reasons  why  separators  are  not  used  in  Portland  Cement  Works." 
E.  C.  Eckel,  Engineering  News,  Vol.  1,1.,  p.  344. 


156  PORTLAND  CEMENT 

materials  and  clinker  in  a  cement  mill.  It  is  compiled  from 
results  obtained  in  actual  practice  and  the  output  of  the  various 
machines  is  the  average  for  long  periods  of  time  and  includes 
shutdown  for  ordinary  repairs,  etc.  For  instance,  when  the 
capacity  of  a  No.  6  Gates  crusher  is  given  as  30  to  40  tons  per 
hour  it  means  that  this  size  crusher  will  crush  300  tons  day  in 
and  day  out  of  ten  hours,  and  not  just  30  tons  for  a  test  run  of  an 
hour.  Similarly,  when  the  capacity  of  a  No.  8  ball  mill  is  given 
at  20  barrels  an  hour  it  means  that  three  of  them  will  safely  take 
care  of  the  clinker  end  of  a  i,2OO-barrel  plant,  allowing  for 
shutdowns  to  clean  and  renew  screens,  put  in  new  plates,  etc. 
In  each  case  the  lower  figure  in  the  table  is  the  safe  one  to  assume 
as  the  least  capacity  of  the  mill  in  question  when  properly  handled. 

The  fineness  of  the  product  is  an  important  item  in  determin- 
ing the  output  of  a  mill.  In  one  instance  which  the  writer 
recently  observed,  a  tube  mill  ground  cement  on  an  average  12 
barrels  an  hour  to  a  fineness  of  97  per  cent,  through  a  No.  100 
sieve  and  on  increasing  the  feed,  15  barrels  an  hour  to  a  fineness 
of  92  per  cent,  passing  a. No.  100  sieve,  or  an  increase  of  3  barrels 
an  hour,  or  25  per  cent,  more  for  a  decrease  of  5  per  cent,  in 
fineness.  In  making  comparisons  between  two  forms  of  grinders, 
therefore,  it  is  necessary  that  the  fineness  of  the  product  produced 
by  each  should  be  the  same,  not  only  when  tested  by  the  No.  100 
sieve  but  also  by  the  No.  200,  as  a  difference  of  2  per  cent,  in! 
fineness  may  easily  represent  a  difference  of  10  per  cent,  in  out- 
put. 

Another  important  fact  which  determines  the  output  of  any 
form  of  granulator  or  pulverizer  is  the  size  of  the  material  fed 
to  the  mill.  Thus  a  tube  mill  fed  with  the  product  from  a  ball 
mill  fitted  with  14-mesh  screens  will  not  pulverize  as  much  as  it 
would  if  the  ball  mill  had  i6-mesh  screen,  etc. 

Degree  of  Fineness  of  the  Raiu  Materials. 

Three  variables  enter  into  the  production  of  Portland  cement 
clinker,  viz: — temperature  of  burning,  length  of  time  in  the  kiln 
and  the  fineness  to  which  the  raw  materials  have  been  reduced. 
This  may  be  expressed  mathematically  as  an  equation  thus,  A  + 


GRINDING   RAW    MATERIAL   AND    MACHINERY 


157 


If 

:  :  :  '     o  o 

o  o      o  o      o      o       • 

I  s 

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sg 

M  vo         tO         O         JO 

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=            S-S    -° 

.  .  .  .      .  . 

32         •    • 

1 

2            c 

s.     B 

00    0 

3 

a 

§                    B 
3                   «  >J       « 

0            SX     5 

«O  O    O    iO 
ro  iO  ON  N        VO  CO 

O   O   O   O         O   O 

VO  CO          N   iO       CO        OO 

o  o      o  o      o     3       • 

if  ' 

£2    ^ 

0 

SScgg,    *-° 

rf  IO        XN   fO        VO          VO 

|g 

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i*f  i 

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rO-3-CC    «          >0  t^ 
0000         00 

o  o      o  o      o      o      o 

i.-—       D 

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o  o      o  o      o      o      o 

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<uj£      « 
O 

•    •    •    •       25 
....       53 

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ill 

s 

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d  d  d  o"      d  d 

v 
v^    O 

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^^,                ^    ^ 

5-0  2     «s-5 
s  s  t     s-co 

1>    Cg    i/           *^ 

1 

IM 

0 

1 

yratory  crusher2  \ 

113  i 

»o  < 

s 

bo     ^     .T: 

s      3     |     S 
S          S       3      a      S 

x>ut  double  this  power  is  req 
•oduct  passing  a  2"  screen  fo 
;d  with  product  of  crusher  or 
or  the  tube  mill, 
•d  with  product  of  ball  mills, 
•d  with  clinker  or  rock  crush 
;d  with  material  from  No.  5  < 

be           •= 

1        = 
o        S 

E       Bill 

^       *  •  .  ••*    1  •  -S 

3         'C        "3       q     •- 

H         O       fa     W     ^ 

«J  ft.  &  u  -j.  &,  ft, 

V 

a 

158  PORTLAND  CEMENT 

B  +  C  =  D,  in  which  A  represents  time:  B,  temperature;  C, 
fineness  and  D,  a  constant  namely,  clinker.  If  we  increase  any 
one  of  the  three  variables  A,  B  and  C,  it  will  decrease  one  or  both 
of  the  other  two.  Thus  by  increasing  the  time  in  the  kiln,  we  de- 
crease the  temperature  necessary  to  clinker  while  if  we  grind  the 
materials  more  finely  we  decrease  either  the  temperature  or  the 
length  of  time  in  the  kiln  and  may  thus  increase  the  output  of  the 
kiln  and  decrease  the  fuel  required  per  barrel. 

In  Portland  cement  clinker  no  actual  fusion  has  taken  place, 
merely  sintering  or  diffusion  between  the  elements  of  the  lime- 
stone and  clay.  That  is  the  silica  and  alumina  in  the  clay 
particles  diffuse  into  the  lime  of  the  limestone  and  vice  versa. 
The  rate  or  rapidity  of  diffusion  as  well  as  the  temperature  at 
which  it  takes  place  depend  upon  the  surface  exposed.  This 
is  a  general  law  applicable  to  all  solids  and  solutions,  therefore, 
the  finer  the  raw  materials  are  ground,  the  greater  area  of 
surface  is  presented  and  consequently  the  greater  chance  for 
diffusion. 

The  actual  degree  of  fineness  to  which  the  raw  material  should 
be  ground  depends  largely  upon  conditions.  It  may  be  said  as  a 
general  rule  that  it  should  never  be  ground  coarser  than  90 
per  cent,  through  a  loo-mesh  sieve  and  that  in  most  cases  95 
per  cent,  to  98  per  cent,  is  required  to  produce  a  sound  cement. 
The  fineness  of  the  raw  material  should  be  tested  at  least  once  a 
day  and,  if  possible,  two  or  three  times  a  day  in  order  to  have  a 
check  upon  the  work  of  the  mills  and  to  keep  them  up  to  standard. 
The  raw  material  can  be  tested  on  the  loo-mesh  sieve  by  the 
method  for  fineness  outlined  in  the  chapter  on  "Physical  Testing." 

In  general  it  may  be  said  that  most  of  the  trouble  experienced 
in  making  a  satisfactory  product  by  cement  mills  is  due  to  im- 
proper grinding  of  the  raw  materials.  Fine  grinding  of  the  raw 
materials  will  always  pay  as  it  reduces  not  only  the  coal  required 
for  burning  but  also  increases  the  output  of  the  kilns  and  results 
in  a  greatly  improved  product. 

Conveyors. 
The  material  is  usually  conveyed  from  one  part  of  the  mill  to 


GRINDING  RAW    MATERIAL  AND   MACHINERY  159 

another  by  mechanical  means.  The  product  of  the  Gates  crusher 
is  carried  to  the  ball  mill  bins  or  the  rolls  on  belt  conveyors  or 
scraper  conveyors,  and  the  fine  material  from  the  ball  mills  and 
the  tube  mills  is  conveyed  by  means  of  screw  conveyors.  The 
elevating  is  done  by  bucket  elevators  of  the  link  belt  form. 
Slurry  and  marl  are  pumped,  using  either  the  compressed  air 
system  mentioned  before  or  a  plunger  pump  of  special  design 
for  the  work.  Dry  material  is  stored  in  steel  bins  at  every  stage 
of  the  process  in  order  to  have  a  constant  supply  for  each  unit 
of  the  grinding  system,  and  marl  and  slurry  are  stored  in  con- 
crete vats  or  steel  tanks  and  kept  in  constant  motion  to  prevent 
the  heavier  and  sandy  portions  from  settling  out. 


Chapter  VII. 


BURNING-KILNS  AND  PROCESS. 


Shaft  Kiln. 

The  first  Portland  cement  made  both  in  Europe  and  America 
was  burned  in  upright  or  dome  kilns,  in  which  the  raw  material 
is  moulded  into  bricks  and  charged  alternately  with  layers  of 
coke.  The  kiln  is  unloaded  at  the  bottom  and,  after  the  clinker 
is  drawn,  it  is  carefully  gone  over  by  men  or  boys  and  the  over- 
burned  and  underburned  sorted  out  and  rejected.  The  prop- 
erly burned  clinker  only  is  ground.  These  kilns  are  similar 
to  those  used  for  burning  lime,  and  their  form  is  shown  in  Fig. 
43,  From  their  shape  they  are  also  called  "bottle"  kilns.  They 


Fig.  43.— Dome  kiln. 


are  intermittent  in  action,  that  is  they  must  be  freshly  charged  for 
each  burning.  On  this  account  there  is  considerable  loss  due  to 
the  necessity  of  heating  up  the  kiln  for  each  burning.  Saylor 


BURNING-KILNS    AND     PROCESS 


161 


burned  his  first  Portland  cement  in  these  kilns  and  the  first  mills 
in  the  Lehigh  Valley  all  used  this  form  of  kiln.  In  Europe  where 
the  bricks  were  made  from  the  more  or  less  plastic  mixture  of 
chalk  and  clay  no  difficulty  was  experienced  in  forming  the 
bricks;  in  this  country,  however,  the  fine  crystalline  cement-rock 
did  not  have  sufficient  binding  power  of  itself  to  make  bricks  of 
the  strength  to  withstand  the  weight  of  the  charge  above  them 
in  the  kilns,  and  it  was  found  necessary  to  incorporate  with  it 
a  small  proportion  of  Portland  cement,  to  give  it  binding  power. 
At  the  American  Cement  Co.'s  plant  at  Egypt,  Pa.,  the  fine 
powder  was  mixed  with  liquid  hydrocarbons  to  form  a  stiff  paste, 
which  was  moulded  by  compression  into  bricks.  This  process 
saved  drying  the  bricks  and  promised  well,  when  the  introduction 


Fig.  44. — Johnston  kiln. 

of  water  gas  raised  the  price  of  coal  tar,  and  necessitated  the 
abandonment  of  the  scheme. 

The  first  efforts  made  to  improve  the  "bottle"  kiln  were  natu- 
rally to  use  the  waste  heat  in  the  products  of  combustion  coming 
off  at  the  mouth  of  the  kiln  for  drying  the  bricks.  Fig.  44  shows 
the  form  of  kiln  invented  in  1872,  by  Mr.  I.  C.  Johnston,  of 
Greenhithe,  England,  for  this  purpose.  A  is  the  kiln  and  B  is  tfie 
drying  chamber.  The  kiln  is  charged  with  the  bricks  which  have 
been  dried  by  the  heat  of  the  previous  burn.  The  wet  bricks  for 
the  next  charge  are  placed  at  the  same  time,  in  the  tunnel-shaped 
flue  and  the  hot  gases  from  the  kiln  pass  over  and  around  them, 
and  dry  them  thoroughly.  These  kilns  are,  of  course,  more  sat- 
isfactory than  the  ordinary  "bottle"  kiln,  but  they  still  waste  much 
ii 


1 62  PORTLAND  CEMENT 

h$at<  .  The  hot  clinker,  of  course,  carries  off  a  great  deal,  and  the 
gooling  off  of  the  kiln  itself  causes  additional  waste.  These  kilns 
were  installed;  in  the  original  mill  of  the  Western  Portland  Ce- 
ment Co.,  Yankton,  S.  P.  The  time  lost  in  drawing  the  clinker, 
charging  the  kiln  and  heating  it  up,  as  well  as  the  heat  losses,  led 
to  the  design  of  continuous  kilns,  in  which  the  charging  is  car- 
ried on  continuously  at  the  top,  and  the  clinker  is  drawn  off  from 
time  to  time  at  the  bottom.  Among  the  best  known  of  these  kilns 
are  the  Hoffmann  ring  kiln,  the  Schoefer  and  the  Deitsch  kilns, 
the  latter  two  are  modifications  of  the  etagen-ofen  or  kiln  of  sev- 
eral stories.  These  kilns  are  all  economical  of  fuel,  but  all  re- 
quire the  material  to  be  made  into  bricks  for  burning  and  the 
clinker  to  be  sorted. 

The  Hoffmann  kiln  is  shown  in  Fig.  45.  It  consists  of  a  ring 
of  chambers,  built  around  a  large  central  chimney.  Each  cham- 
ber is  connected  with  the  chimney  by  a  flue  and  has  a  door  open- 
ing outwards.  The  chambers  are  also  all  connected  with  each 
other.  The  bricks  are  piled  up  in  the  chambers,  just  as  they  are 
in  a  brick  kiln,  so  that  the  products  of  combustion  can  pass 
around  them  and  between  them.  The  oven  is  operated  as 
follows :  When  a  chamber  is  loaded,  it  is  shut  off  from  the  suc- 
ceeding one,  which  is  empty,  by  a  sheet  iron  door,  and  connected 
with  the  preceding  one.  The  flue  leading  into  the  chimney  is 
also  opened  and  the  corresponding  flue  in  the  preceding  cham- 
ber is  closed.  By  this  means,  the  waste  heat  from  the  compart- 
ment, whose  contents  is  being  burnt,  is  passed  forward,  around 
the  ring  of  compartments,  to  the  one  just  charged,  and  thence 
through  the  flue  and  up  the  chimney.  By  this  means  the  con- 
tents of  the  chambers  are  gradually  heated  up,  the  bricks  are 
dried  in  the  chambers  near  the  flue  and  then  become  hotter  and 
hotter  as  the  chamber  of  combustion  is  brought  nearer.  The 
air  for  burning  is  passed  through  the  chambers  in  which  burning 
is  completed  and  is  thereby  itself  heated  and  the  clinker  cooled. 
It  is  usual  to  load  one  compartment  each  day,  and  of  course,  to 
draw  one.  The  fuel  for  burning  is  not  loaded  in  with  the  bricks, 
but  is  fed  in  from  openings  at. the  top  of  the  kiln  during  burning. 
The  Hoffmann  kiln  is  very  economical  of  fuel,  but  requires  much 


BURNING-KILNS    AND    PROCESS 


I63 


skilled  labor  if  it  is  to  be,operated  successfully.  The  bricks  have 
to  be  carefully  piled  and  the  charging  requires  skilled  hands. 
This  kiln  is  much  in  use  in  Germany,  but  so  far  as  the  writer 


Fig.  45. — Hoffmann  ring  kiln. 

knows,  has  never  been  used  in  this  country  for  burning  Portland 
cement. 

The  Dietsch  kiln  is  shown  in  Fig.  46.  It  was  patented  in  1884. 
It  consists  of  a  cooling  chamber  H,  a  burning  chamber  F  and  a 
heating  chamber  C.  The  kilns  are  usually  built  in  pairs,  back  to 
back.  The  kiln  is  loaded  through  the  door  A,  and  as  clinker  is 
drawn  out  at  the  bottom,  the  dry  slurry  drops  down  into  the  heat- 
ing chamber  where  it  is  gradually  brought  up  to  a  high  tempera- 
ture. From  the  heating  chamber  it  is  raked  over  into  the  com- 
bustion chamber,  by  introducing  a  tool  in  the  door  B,  and  fuel 


Fig.  46.— Dietsch  kiln. 


BURNING-KILNS    AND    PROCESS 


for  the  burning  is  mixed  with  it  through  the  same  door.  The 
burning  is  completed  in  F.  The  cold  air  for  combustion  is  heated 
by  passing  through  the  red  hot  clinker  in  H,  cooling  the  latter. 
Eyes  are  placed  at  the  lower  levels  of  the  combustion  chamber, 


Fig.  47. — Schoefer  kiln. 

through  which  bars  may  be  inserted  to  detach  the  sintered  mass 
should  it  hang  up,  due  to  overburning.  The  Dietsch  kiln  is  also 
economical  of  fuel,  but  requires  that  the  slurry  be  made 
into  bricks.  Several  were  introduced  into  this  country  in  the 


1 66  PORTLAND  CEMENT 

early  days  of  the  industry,  one  being  built  for  the  Buckeye  Ce- 
ment Co.,  of  Bellefontaine,  O.  A  modification  of  the  Dietsch 
kiln  perfected  in  Denmark  and  known  as  the  Schoefer  kiln,  was 
introduced  into  several  of  the  earlier  cement  mills  and  was  used, 
I  believe,  by  the  Glens  Falls  Portland  Cement  Co.,  Glens  Falls, 
N.  Y.,  exclusively,  and  also  by  the  Coplay  Cement  Co.,  at  one  of 
their  mills,  at  Coplay,  Pa.,  where  eleven  were  once  in  use.  The 
Schoefer  kiln  is  shown  in  Fig.  47.  It  operates  upon  the  same 
principle  as  the  Dietsch  kiln  and  consists  of  a  long  vertical  flue, 
the  upper  part  of  which  serves  as  a  preheating  chamber,  the 
middle  narrow  part  as  a  combustion  chamber  and  the  lower  sec- 
tion to  heat  the  draft. 

With  all  these  kilns  the  product  has  to  be  sorted  and  the 
underburned  portions  picked  out  and  reburned.  They  are  also 
troubled  with  dusting  clinker : — that  is,  clinker  which  falls  to  a 
powder  on  cooling.  This  fault  is  supposed  to  be  caused  by 
changes  in  the  structure  of  the  clinker  brought  about  by  too  slow 
cooling  of  the  latter.  These  shaft  kilns  require  only  about  45 
pounds  of  coal  per  barrel,  but  the  labor  cost  connected  with  them 
is  two  or  three  times  as  great  as  the  fuel  cost.  The  shaft  kilns 
themselves  cost  in  proportion  to  their  output  of  clinker  about 
twice  as  much  as  a  rotary  kiln. 

The  Rotary  Kiln. 

The  kilns  above  described  are  still  used  largely  in  Germany; 
in  France  and  Belgium,  the  Candlot  and  Bauchere  kilns  are  used, 
and  in  England  the  Johnston  kiln  is  much  employed.  In  this 
country  the  cost  of  moulding  the  raw  material  into  bricks  was 
considerable,  and  the  sorting  of  the  clinker,  made  necessary  by 
the  uneven  burning  in  these  kilns,  further  increased  the  cost  of 
manufacture.  Abroad  where  labor  is  much  cheaper  than  it  is 
in  this  country,  these  operations  could  be  carried  on  successfully, 
so  that  European  cements  could  be  brought  to  this  country  and 
sold  in  competition  with  American  cements  at  a  good  profit. 
Their  reputations  were  established  and  they  could  successfully 
hold  their  market  against  the  home  manufacturers,  who  could  not 
afford  to  cut  the  price  of  their  cement  owing  to  the  high  cost  of 


BURNING-KILNS    AND     PROCESS  167 

manufacturing  due  to  the  expensive  labor  item,  so  that  all  the 
early  manufacturers  were  seeking  a  cheaper  method  of  burning, 
one  that  would  do  away  with  the  employment  of  so  much  hand 
labor  and  allow  them  to  compete  successfully  with  their  foreign 
rivals.  This  led  them  to  experiment  with  the  rotary  kiln  which 
had  been  invented  in  1873  by  F.  Ransom,  an  English  engineer, 
but  which  had  never  been  successfully  used  in  England.  In 
this  country  the  first  plant  to  attempt  its  use  was  a  small  plant 
in  Oregon,1  in  1887,  but  the  attempt  proved  a  failure  and  the 
plant  itself  was  shut  down,  owing  to  litigation  among  its  stock- 
holders. About  the  same  time  the  Atlas  Portland  Cement  Co. 
began  to  experiment  with  Ransom's  kiln,  first  at  East  Kings- 
ton, New  York,  on  wet  materials  and  later  with  success  upon  the 
cement-rock  of  the  Lehigh  District,  at  Northampton,  Pa.  At 
first  they  met  with  many  difficulties,  and  it  was  only  after  much 
experimenting,  that  they  succeeded  in  making  it  work  success- 
fully. They  found  that  owing  to  the  shorter  time  during  which 
the  material  underwent  calcination,  it  was  necessary  to  grind  it 
much  finer  than  had  been  necessary  with  the  old  bottle-shaped 
kilns.  They  also  found  it  necessary  to  carry  the  lime  a  little 
higher,  in  their  raw  material  than  had  been  done  before,  and  to 
moisten  it  slightly  with  water.  In  Ransom's  original  patent  he 
proposed  to  heat  the  kiln  by  producer  gas,  but  its  development 
in  this  country  was  made  possible,  by  the  use  of  crude  oil,  as  a 
successful  method  of  burning  powdered  coal  had  not  been  per- 
fected at  that  time.  At  first  these  kilns  were  only  40  feet  long, 
but  it  was  found  more  economical  to  lengthen  them,  from  60  to 
150  feet  being  now  the  usual  lengths  with  125  as  the  average 
at  the  newer  plants. 

Mechanical  Construction. 

The  rotary  kiln  in  its  usual  form  consists  of  a  cylinder,  from 
6  to  8  feet  in  diameter  by  from  60  to  150  feet  long,  made  of  steel 
sheets  from  y2  to  9/16  inch  in  thickness,  lined  with  fire  brick 
and  inclined  at  a  pitch  of  from  ^  to  ^  inch  to  the  foot.  The 
steel  sheets  are  held  together  with  single  strap  butt  joints,  as 

1  Mineral  Resources,  U.  S.  Geol.  Survey,  1887,  p.  530. 


l68  PORTLAND  CEMKNT 

these  joints  resist  expansion  strains  due  to  heating  better  than 
lap  joints.  This  cylinder  is  supported  at  a  very  slight  angle  from 
the  horizontal  on  two  or  more  tires  made  of  rolled  steel,  and  hav- 
ing a  face  of  from  6  to  12  inches  and  a  thickness  of  at  least  4 
inches.  These  tires  are  not  fastened  directly  to  the  kiln,  but  are 
held  2  to  6  inches  from  the  latter  by  an  arrangement  of  blocks 
and  plates.  They  run  each  on  heavy  friction  rollers  which  are  often 
mounted  in  pairs  on  a  rocker  and  made  of  cast  steel.  The  kiln 
is  driven  by  a  girth  gear  situated  usually  near  its  middle,  and  a 
train  of  gears,  actuated  either  by  a  line  shaft  or  a  motor.  The 
upper  end  of  the  kiln  projects  into  a  brick  flue  which  is  sur- 
mounted by  a  steel  stack.  The  flue  is  provided  with  a  door  at 
the  bottom  to  take  out  the  dust  which  accumulates  there. 

The  lower  end  of  the  kiln  is  closed  by  a  hood  into  which  the 
kiln  projects.  Some  times  this  hood  is  made  stationary  with 
movable  fire  brick  doors,  but  oftener  it  is  mounted  on  a  movable 
carriage.  The  front  wall  of  the  hood  is  provided  with  two  holes, 
one  for  the  entrance  and  support  of  the  burning  apparatus,  and 
the  other  for  observing  the  operation  of  the  kiln  and  for  insert- 
ing bars  to  break  up  the  rings  formed  and  repair  the  lining.  The 
lower  part  of  the  hood  is  left  partly  open  and  through  this  the 
clinker  falls.  Air  for  combustion  also  enters  here.  Figs.  48,  49.  60 
and  61  show  as  well  as  can  be  done  in  a  small  illustration  of 
such  a  long  object  the  construction  of  the  completed  kiln. 

The  usual  diameter  of  a  6o-foot  rotary  kiln  unlined  is  from 
6  to  7  feet,  of  a  100  foot  rotary  from  7  to  8  feet  and  of  a  125  foot 
rotary  8  to  8^2  feet.  Most  of  them  are  made  the  same  diameter 
throughout,  though  some  of  them  are  made,  say  6  feet  6  inches 
in  diameter  for  the  first  30  feet  and  then  taper  through  10  feet 
to  a  diameter  of  5  feet  6  inches  for  the  remaining  20  feet ;  others 
taper  for  the  last  10  or  15  feet  before  entering  the  stack.  This 
latter  plan  has  the  effect  of  a  damper,  crowding  the  heat  more 
to  the  front  of  the  kiln.  It  probably  lessens  the  output  some- 
what, since  the  choking  cuts  down  the  amount  of  coal  that  can 
be  burned. 

The  short  60  foot  kilns  usually  bear  upon  two  or  three  tires, 


BURNING-KILNS    AND    PROCESS  169 

while  the  longer  ones  bear  on  from  two  to  five.     There  are  al- 


ways provided  two  or  more  horizontal  thrust  roller  bearings  to 
keep  the  kiln  on  the  vertical  roller  bearings. 


170 


PORTLAND  CEMENT 


Feeding  in  the  Raw  Material. 

Dry  material  is  fed  into  the  kiln  by  means  of  an  inclined  spout 
or  a  water-jacketed  screw  conveyor  running  from  the  kiln  bins, 
which  are  situated  usually  over  or  just  back  of  the  flue,  through 
the  latter,  far  enough  into  the  kiln  to  prevent  the  materials  falling 
into  the  flue  when  the  kiln  revolves.  The  feeding  device  is 


Fig.  50.— Stock  bins  and  water-jacketed  conveyor  for  feeding  raw  material  into  kiln. 

usually  attached  to  the  driving  gear  of  the  kiln,  so  that  when  the 
latter  stops  the  feed  is  shut  off.  When  slurry  is  used,  this  is 
pumped  into  the  kiln  from  a  vat  below,  by  either  a  plunger  pump 
or  compressed  air.  In  some  instances,  it  is  pumped  against  the 
pressure  of  a  standpipe,  to  insure  a  constant  feed. 

Fig.  50  shows  an  arrangement  designed  by  the  Allis-Chalmers 


BURNING-KILNS    AND    PROCESS 


171 


Co.  for  feeding  the  material  into  the  kiln  by  means  of  a  water- 
jacketed  conveyor.  This  plan  is  now  considered  inferior  to 
the  method  of  spouting  the  material  into  the  kiln.  Fig.  51  shows 
he  arrangement  generally  employed  where  the  latter  plan  .for  in- 
troducing the  material  into  the  kiln  is  followed.  It  will  be  noticed 
that  the  bins  are  located  above  the  kilns.  This  saves  room.  The 


m 


Fig.  51. — Method  of  feeding  raw  material  into  the  kiln  by  means  of  a  spout. 

long  conveyor  leading  from  the  bins  to  the  hopper  spout  in- 
sures a  regular  feed  of  material  to  the  kiln.  The  stack  is  set 
to  one  side  of  the  center  line  of  the  kiln  which  gives  the  dust  a 
chance  to  settle.  The  spout  is  of  cast  iron  pipe. 

Speed  of  Rotation. 

The  kilns  are  rotated  in  different  mills  at  different  speeds, 
varying  from  one  turn  in  one-half  a  minute  to  one  turn  in  three. 
|The  average,  however,  is  from  a  turn  in  a  minute  and  a  half  to 
one  in  two  minutes.  The  speed  varies  somewhat  with  the  angle 
at^which  the  kiln  is  pitched,  the  greater  the  pitch  the  slower  the 
speed  as  the  steeper  the  angle  of  the  kiln  the  greater  distance  the 


172  PORTLAND  CEMENT 

material  will  travel  with  each  revolution.  Usually  the  speed  can 
be  regulated  by  some  arrangement  of  an  automatic  speeder,  such 
as  the  Reeves,  the  Mosser  speeder  or,  where  run  from  separate 
motors.,  by  a  controller.  In  some  mills  all  the  kilns  are  on  one 
shaft  and  consequently  of  fixed  speed.  There  are  some  points  in 
favor  of  each.  Where  the  speed  can  be  regulated  by  the  burner, 
he  has  better  control  of  the  burning,  but  there  is  sometimes  a 
tendency  on  his  part,  where  the  foreman  is  lax,  to  cut  down  the 
speed  and  consequently  the  capacity  of  the  kiln  in  order  to  make 
his  own  work  easier.  Where  there  is  a  likelihood  of  the  mix  not 
being  regular,  speeders  should  always  be  put  in,  as  it  is  easier 
to  control  the  burning  of  such  material  by  the  kiln  speed  than  by 
the  coal  feed.  With  fixed  speed,  the  kilns  are  arranged  with 
some  sort  of  jaw  clutch,  so  they  can  be  cut  out  for  patching,  re- 
lining,  etc.  It  is  also  necessary  occasionally  to  shut  them  down 
for  "heat"  if  the  mixture  burns  hard,  or  the  raw  material  is  fed 
into  the  kiln  irregularly,  causing  it  to  become  overloaded.  As 
we  have  said,  the  raw  material  fed  into  the  kiln  should  be  con- 
trolled by  the  speed  of  the  latter  and  be  shut  off  when  the  kiln 
stops. 

Most  of  the  newer  mills  are  installing  individual  motor  drives 
for  their  kilns,  employing  for  this  purpose  slow  variable  speed 
motors.  A  6'  X  60'  kiln  requires  about  5  H.  P.  and  one 
8'  X  125',  20  H.  P. 

A  great  deal  has  been  said  about  the  proper  speed  for  a  kiln 
to  revolve,  no  two  authorities  agreeing,  and  the  writer  has  come 
to  the  conclusion  from  personal  experience  that  this  will  depend 
largely  upon  the  material,  how  it  burns,  etc.  If  the  kiln  is  run 
at  a  high  speed,  the  material  travels  through  in  a  thin  stream  and 
remains  in  the  kiln  but  a  short  time.  On  the  other  hand,  it  is 
being  continually  turned  over  and  exposed  to  the  hot  kiln  gases 
and  kiln  lining,  so  that  while  the  time  of  heating  is  shorter  the 
chances  of  absorbing  heat  are  greater. 

Kiln  Lining. 

The  rotary  kiln  as  has  been  said  is  lined  with  fire  brick.  This 
brick  should  be  of  the  most  refractory  kind.  I  believe  at  one 


BURNING-KILNS    AND    PROCESS  173 

time  a  magnesia  brick  was  used  but  now  a  good  quality  fire  brick 
is  considered  as  satisfactory  and  more  economical  than  the 
expensive  magnesia  lining.  A  good  fire  brick  should  analyze 
within  these  limits  : — 

Per  cent. 

Silica,  SiO2 45-°    to    50.0 

Alumina,  A12O3 '• 43-Q    to    48.0 

Iron,  Fe2O3 Less  than  3.0 

Magnesia,  MgO Less  than  0.5 

Lime,  CaO Less  than  0.5 

It  should  also  be  free  from  iron  and  alkalies,  since  these  cause 
fusibility.  A  fire  brick  lining  should  last,  if  carefully  attended 
to,  at  least  9  to  12  months  and  sometimes  they  go  even  longer 
than  this.  At  the  end  of  this  time  the  bricks  are  eaten  away  nearly 
to  the  iron  shell  and  it  becomes  necessary  to  cut  away  the  brick 
from  the  first  20  or  30  feet  of  the  kiln  and  reline  this  portion. 
The  upper  part  of  the  kiln  lining,  or  that  portion  of  it  which 
merely  comes  in  contact  with  the  powdered  raw  material  before 
sintering  commences,  usually  lasts  indefinitely.  In  kilns  work- 
ing on  wet  materials  it  is  sometimes  the  practice  to  leave  the  up- 
per 20  or  25  feet  of  the  kiln  unlined  since  this  part  of  the  kiln  is 
kept  fairly  cool  by  the  wet  slurry.  Sometimes  channel  irons  or 
Z  bars  are  fastened  to  the  sides  of  the  kiln  to  form  shelves  for 
drying  the  material. 

A  bauxite  or  alumina  brick,  manufactured  by  the  Laclede- 
Christy  Clay  Products  Co.,  St.  Louis,  Mo.,  has  been  extensively 
used  in  the  west  and  middle  west  for  lining  Portland  cement  kilns 
and  it  is,  in  that  section  at  least,  considered  superior  to  the  silica 
brick 

In  place  of  fire  brick  a  concrete  or  clinker  brick  made  from 
Portland  cement  clinker  and  Portland  cement  is  used.  The  clink- 
er should  be  screened  and  that  portion  of  it  passing  a  %  inch 
screen  used.  This  is  mixed  with  Portland  cement  in  the  propor- 
tions of  thirty  parts  clinker  to  twelve  parts  cement  and  made 
into  a  medium  wet  concrete.  .This  is  then  rammed  into  wooden 
forms  of  the  proper  size  and  shape  and  allowed  to  harden.  The 
bricks  are  ready  for  use  several  days  after  making.  One  large 
mill  in  the  Lehigh  District  used  these  bricks  exclusively  at  one 


174  PORTLAND  CEME-NT 

time  for  lining  the  clinkering  zone  of  their  kilns,  and  found  them 
very  satisfactory.  Under  conditions  in  this  region,  however,  they 
do  not  seem  to  be  any  cheaper  than  fire  brick.  They  also  do 
not  stand  up  well  where  the  kiln  is  not  run  continuously. 

The  fire  bricks  used  to  line  the  lower  end  of  the  kiln  are  usual- 
ly from  9  to  12  inches  thick,  and  those  for  lining  the  upper  end, 
from  4  to  6  inches.  These  bricks  are  keyed  to  fit  the  circle  of 
the  kiln. 

It  is  sometimes  the  practice  to  place  a  lining  of  sheet  asbestos 
between  the  fire  brick  lining  and  the  steel  shell.  This  protects 
the  tires,  and  also  the  shell,  to  some  extent,  as  it  cuts  off  some  of 
the  heat  transmitted  to  the  latter.  The  writer  has  used  an  asbes- 
tos lining  several  time  and  found  that  it  unquestionably  cuts  off 
some  heat  from  the  shell  but  decreases  the  life  of  the  lining. 
For  an  asbestos  lining,  Y^  inch  board  is  usually  used. 

Prof.  Landis,  of  Lehigh  University,  claims  that  the  radiation 
losses  in  a  rotary  kiln  amount  to  30  per  cent,  of  the  total  coal 
burned,  and  proposes  using  a  lining  of  some  good  non-conductor 
of  heat  between  the  shell  and  the  fire  brick.  If  all  of  the  heat 
was  confined  to  the  lining  and  the  latter  not  allowed  to  cool  by 
radiation  it  is  doubtful  if  the  lining  would  last  as  long  as  it  now 
does. 

In  the  old  upright  kilns,  it  was  the  usual  practice  to  coat  the  lin- 
ing of  the  kiln  with  a  "grout"  of  slurry,  so  that  it  was  natural  for 
something  of  the  same  sort  to  be  tried  upon  the  rotary  kiln.  It 
was  soon  found  that  a  certain  amount  of  the  raw  material  could 
be  made  to  adhere  to  the  fire  bricl$  lining  of  the  kiln,  thereby  re- 
moving the  bricks  from  the  scorifying  action  of  the  caustic  clink- 
er. It  is  now  the  practice  to  burn  entirely  on  coated  bricks. 
When  this  coating  falls  off,  usually  only  in  patches,  the  kiln  is 
heated  up  above  the  normal  temperature,  raw  material  is  scraped 
down  over  the  bare  spot  and  pounded  into  place  with  a  heavy 
iron  bar.  Water  is  then  usually  run  on  the  "patch"  to  harden  it. 
In  some  mills  salt  is  used  on  the  bare  spot,  as  it  is  supposed  to 
make  the  patch  hold  better.  The  writer  has  never  seen  any  ad- 
vantage in  its  use,  however. 

The  fire  brick  are  held  in  the  kiln  by  a  heavy  angle  iron  run- 


BURNING-KILNS    AND    PROCESS  175 

ning  around  both  ends  of  the  kiln.     This  also  helps  to  stiffen  the 
kiln  shell. 

Labor. 

The  operation  of  Portland  cement  burning  is  essentially  a  skill- 
ed process  and  a  skilled  workman  is  required  to  attend  it.  He 
must  know  just  how  the  clinker  should  be  burned  and  have  a  good 
eye  for  "heat,"  so  that  he  can  tell  when  his  kilns  are  hot  enough 
to  clinker  the  raw  material  properly.  The  placing  of  the  patches 
and  the  coating  of  a  freshly  lined  kiln  also  require  some  skill.  To 
be  economically  run  the  kilns  should  be  kept  at  as  nearly  a  uni- 
form temperature  as  the  irregularity  of  the  feeding  devise  will 
permit.  Kilns  run  spasmodically,  first  hot,  then  cold,  require 
much  coal,  turn  out  poorly  burned  clinker,  and  require  much 
patching.  Since  patching  requires  the  stopping  of  the  kiln  the 
output  is  also  cut  down. 

The  burner  should  also' be  a  sufficiently  good  mechanic  to  look 
after  the  mechanical  part  of  his  kilns.  One  burner  usually  looks 
after  two  to  four  kilns.  The  operations  of  the  interior  of  the 
kiln  are  watched  through  darkened  glasses.  No  efforts  have 
been  made  to  use  pyrometers  since  the  temperature  must  change 
with  the  refractoriness  of  the  material,  etc.  and  the  heat  is  entire- 
ly judged  by  the  incandescence  of  the  interior  of  the  kiln  and 
the  clinker  as  observed  through  these  glasses. 

The  method  of  injecting  the  fuel  into  the  kiln  and  the  prepara- 
tion of  the  powdered  coal  are  described  in  the  next  chapter.  , 

Capacity  and  Fuel  Consumption. 

The  table  below  gives  the  output  and  fuel  consumption  of 
rotary  kilns  of  various  dimensions.  This  amount  includes  c(>al 
used  for  heating  the  kiln  after  patching  and  the  usual  shut- 
downs and  delays  met  with  in  every  mill.  The  figures  are 
merely  average  ones  and  with  certain  raw  materials  or  under 
certain  favorable  conditions  the  output  may  vary  25  per  cent. 
either  way  from  the  figures  given.  The  quality  of  the  coal  of 
course  has  an  important  bearing  on  the  quantity  used.  The 
figures  in  the  table  are  for  coal  containing  14,000  B.  t.  u.  per 
pound.  If  the  coal  to  be  used  contains  less,  the  comparison 


176 


PORTLAND   CEMENT 


may  be  made  on  a  numerical  basis.  That  is  if  a  coal  contains 
only  10,000  B.  t.  u.,  140  Ibs.  of  it  will  be  required  to  do  the 
burning  which  100  Ibs.  of  the  higher  value  coal  on  which  the 
table  is  based  would  do. 


TABLE  XIV. — CAPACITY  AND  COAL  CONSUMPTION  OF    ROTARY  KILNS. 


Dimensions  of  kiln 

Capacity  in  barrels 

Coal  Consumption 

Length 

Diameter  1 

Dry  process 

Wet  process 

Dry  process 

Wet  process 

60 

6 

2OO 

140 

110 

150 

80 

6 

250 

1  80 

100 

135 

100 

7 

400 

300 

90 

110 

125 

8 

600 

45° 

80 

150 

9 

750 

80 

Chemical  Changes  Undergone  in  Burning. 

The  changes  undergone  during  burning  may  be  summed  up  as 
follows : 

The  carbon  dioxide,  existing  in  the  raw  material  in  combina- 
tion with  the  lime  and  magnesia  as  carbonate  of  these  elements, 
is  practically  entirely  expelled.  Even  the  little  which  exists  in 
freshly  ground,  well  burned  cement  is  probably  most  of  it  ab- 
sorbed from  the  air,  since  cement  very  rapidly  absorbs  carbon 
dioxide  and  water. 

All  of  the  water  originally  present  whether  free,  hydroscopic 
or  combined  is  driven  off  and  the  carbon  and  organic  matter  in  the 
raw  material  are  also  burned  away.  The  iron,  the  greater  part  of 
which  is  usually  present  in  clay  and  cement-rock  in  the  ferrous 
condition  is  almost  completely  oxidized. 

The  sulphur  whether  present  in  the  raw  material  as  sulphide, 
sulphate  or  in  combination  with  organic  matter  is  much  of  it  ex- 
pelled and  the  remainder  is  usually  all  of  it,  except  a  mere  trace, 
found  present  as  calcium  sulphate.  This  is  to  be  expected  since 
calcium  sulphate  gives  off  its  sulphuric  acid,  when  heated  with 
silica.  Indeed,  I  believe  it  has  been  proposed  to  make  cement 

1  Of    shell,  lining  of  9"  bricks. 


BURNING-KILXS     AND     PROCESS  177 

by  heating  together  a  mixture  of  clay  and  gypsum,  the  sulphuric 
anhydride  driven  off  during  the  process  being  caught  and  con- 
densed with  water  and  sold  for  sulphuric  acid.  It  has  also  been 
supposed  that  the  sulphur  of  the  coal  entered  the  clinker.  This 
is  erroneous,  since  the  amount  of  gas  slack  necessary  to  burn 
TOO  Ibs.  of  clinker  will  contain  sufficient  sulphur  to  make  the 
clinker  analyze  at  least  1.5  per  cent.  SO3  if  it  were  all  absorbed, 
while  as  a  matter  of  fact  clinker  seldom  analyzes  anywhere  near 
this  amount. 

The  alkalies,  potash  and  soda  are  partly  expelled  in  the  kiln. 
In  experiments  made  by  the  writer,  which  will  be  detailed  below, 
the  losses  of  soda  amounted  to  from  19  to  28  per  cent.,  while 
those  of  potash  ran  from  46  to  52  per  cent.  W.  F\  Hillebrand,  of 
Washington,  D.  C.,  applied  for  a  patent  on  a  process  for  con- 
densing these  alkalies,  looking  to  their  utilization  as  fertilizers. 
This  loss  of  alkali  is  also  shown  by  analysis  of  the  deposit  collect- 
ing on  the  walls  of  the  kiln  stack,  a  sample  of  which  contained 

Per  cent. 

Soda 1.38 

Potash 6.83 

In  a  paper  read  by  the  author  before  the  Association  of  Port- 
land Cement  Manufacturers,  the  results  of  an  experiment  to  de- 
termine the  losses  actually  occurring  in  the  rotary  kiln  were 
given.  This  experiment  consisted  in  sampling  carefully  the  raw 
material  going  into  the  kiln,  the  clinker  coming  out  and  the  coal 
used  for  burning.  The  samples  were  taken  every  3  minutes  for 
5  hours.  The  clinker  was  not  sampled  for  45  minutes  after  the 
first  raw  material  sample  was  taken  and  was  collected  for  45 
minutes  after  the  last  raw  material  sample  was  taken;  the  idea 
being  to  allow  the  material  to  work  through  the  kiln  so  that  the 
clinker  represented  the  burned  raw  material.  The  samples  were 
taken  at  kilns  working  normally,  with  a  steady  feed  and  raw 
material  of  constant  composition.  The  samples  were  then  all 
carefully  analyzed.  Three  separate  tests  were  made,  but  only  one 
set  of  results  is  given  here: 

12 


178 


PORTLAND 


Raw 
material 
as 
analyzed 

Clinker 
as 
analyzed 

Raw 
material 
calculated 
to  a 
clinker 

Clinker 
calculated 
without  its 
H2O,  CO2, 
etc. 

Loss 
or 
gain 

Sio  

1  1  AA 

4-67 

TiO  

xO-44 

O  12 

O  12 

-01 

Al  Oo  . 

"•*3 

4   re 

u.o^ 
72Q 

'-'•oo 
6  01 

u.o^ 
712 

uo 

4-1Q 

Fe,0* 

•OO 

Ocfi 

••*y 

2   ^2 

u-yo 

2  14. 

•o-* 
2  66 

i  oy 

4-M 

FeO 

n  88 

••o* 

•«'O4 

1  o^ 

MnO  

o  06 

O  OQ 

O  OQ 

O  OQ 

OO 

CaO  .  . 

u.uy 

61  80 

1  08 

M^O  .  . 

41.04 

Do-oo 

"O*/" 

1  01 

Na  O  .  . 

•V4 

•Vo 

0    l8 

•94 

3*V7 

o  18 

1  uo 

K  O  

u.^i 

0.47 

uy 
,   ,  .,  r  T 

P  O   . 

u.  /z 

uoy 

*joy 

J1 

so   .  . 

U-O4 
o  18 

?7 

1  ?  :.:::..::::::: 

O   11 

*»*o 

c/ 

c  

"•oo 

O  7^ 

con  . 

W«/O 
•70   QA 

O  12 

H2O  •  •  

o^-y4 

I    ^ 

"•o-4 

o  24 

^•oo 

In  the  second  and  third  columns  will  be  found  the  analysis  of 
the  raw  material  and  clinker  respectively.  In  the  fourth  column 
is  calculated  the  composition  the  raw  material  would  have  after 
clinkering  if  the  only  changes  which  took  place  were  the  oxida- 
tion of  the  ferrous  iron  and  sulphur,  the  burning  off  of  the  car- 
bon and  the  volatilization  of  the  carbon  dioxide  and  water.  The 
fifth  column  gives  the  analysis  of  the  clinker  calculated  to  100% 
without  its  water  and  carbon  dioxide  and  after  its  sulphur  and 
iron  had  all  been  calculated  to  SO3  and  Fe2O3  respectively.  The 
coal  used  for  burning  in  the  experiment  was  Fairmont  gas  coal. 

Analysis  of  Fairmont  Gas  Coal: 

Moisture 1.34 

Volatile  and  combustible  matter 34. 1 1 

Fixed  carbon 54.03 

Ash — SiO2 3.59 

TiO2 0.08 

A12O3 1.50 

Fe203 1.91 

MnO 0.03 

CaO 0.75 

MgO 0.03 

Na2O o.  10 

KjO o.  16 

P2O5 0.06 

SO3 0.54 

8.75 
Sulphur 1.77 


BURNING-KILNS    AND    PROCESS  179 

Twenty-nine  pounds  of  this  coal,  the  approximate  quantity 
necessary  to  burn  100  pounds  of  clinker,  will  contain : 

Pounds 

SiO2 1.04 

TiO2 0.02 

A12O3 0.44 

Fe2O3 0.55 

MnO o.oi 

CaO 0.22 

MgO  ....    o.oi 

Na2O 0.03 

K2O 0.05 

P2O5 0.02 

SO3  (total  S  to) 1.43 

If  we  compare  these  figures  with  those  in  the  last  column  of 
the  table,  we  will  see  that  the  silica,  ferric  oxide  and  alumina 
have  been  increased  by  approximately  one-half  the  coal  ash.  Un- 
doubtedly, in  the  rotary  kiln  much  of  the  ash  is  carried  out  with 
the  gases  by  the  strong  draft  of  the  kiln.  This  we  would  expect 
when  we  consider  that  the  particles  of  ash  are  of  the  same  vol- 
ume as  the  particles  of  coal,  and  yet  only  one-tenth  their  weight, 
for  when  the  coal  burns  it  leaves  its  ash  in  the  form  of  a  skeleton. 
These  particles  of  ash  are  already  in  motion  and  are  in  the  full 
draft.  The  gases  have  a  velocity  of  at  least  2,000  feet  per  min- 
ute, which  is  quite  enough  to  carry  the  particles  up  the  chimney. 
It  seems  probable  in  view  of  these  facts  that  what  ash  does  con- 
taminate the  clinker,  comes  from  the  impinging  of  the  flame 
upon  the  material  in  the  kiln.  The  ash  strikes  the  clinker  and 
its  velocity  is  stopped  by  the  impact  and  it  either  falls  among  the 
clinkers  or  it  sticks  to  the  red-hot,  semi-pasty  mass.  It  is  proba- 
ble that  the  coarser  the  coal  the  more  ash  will  contaminate  the 
clinker.  It  is  an  important  point  where  this  ash  falls.  If  it  falls 
before  the  raw  material  begins  to  ball  up,  24  Ibs.  extra  limestone 
should  be  added  to  every  600  Ibs.  of  raw  material  to  take  care  of 
the  ash,  as  in  this  case,  it  would  form  Portland  cement  clinker. 
If,  however,  it  falls  on  the  clinker  after  it  forms  into  balls,  this 
quantity  should  be  very  much  less,  if  any  at  all,  as  its  action  is 
merely  on  the  surface  of  the  clinker  to  form  a  slag  and  not  a  true 
Portland  cement  clinker. 


l8o  PORTLAND  CEMENT 

If  we  recalculate  the  clinker,  taking  into  consideration  the  vola- 
tilizing of  the  sulphur,  potash  and  soda,  and  adding  one-half  the 
elements  introduced  by  the  coal  ash,  we  would  have  a  clinker 
with  the  following  analysis : 

SiO2 21.09 

TiO2 0.36 

A1203 7-17 

Fe2O3 2.62 

MnO 0.09 

CaO 63.99 

MgO •     2.95 

Na2O 0.39 

K2O 0.61 

P205 •••••• 0.35 

S03 0.38 

Comparison  of  these  figures  with  those  of  the  fifth  column 
shows  them  to  be  close  to  our  actual  results. 

Another  point  brought  out  by  these  tests  is  the  loss  of  material, 
as  dust,  etc.,  during  the  pulverizing  and  burning  of  the  raw  mate- 
rial and  clinker.  Allowing  the  losses  shown  for  volatilization  of 
the  soda,  potash,  and  sulphur,  in  the  proportions  shown  in  the 
experiment,  and  adding  one-half  of  the  coal  ash,  100  Ibs.  of  raw 
material  should  make  67.25  Ibs.  of  clinker,  or  565  Ibs.  of  raw 
material  should  make  I  barrel,  or  380  Ibs.  of  clinker.  The  rock 
as  it  comes  from  the  quarry  usually  carries  much  more  moisture 
than  the  analysis  shows,  but  even  taking  an  extreme  of  5  per 
cent,  moisture,  594  Ibs.  should  make  a  barrel  of  clinker.  Few 
manufacturers  use  less  than  610  Ibs.,  showing  a  lost  of  16  Ibs., 
as  dust,  etc.,  per  barrel  of  clinker  produced. 

The  above  changes  are  simply  those  which  we  can  detect  by 
comparative  chemical  analysis  of  the  raw  material  and  the  clink- 
er. None  of  them  is  sufficient  of  itself  to  form  Portland  ce- 
ment. All  the  carbon  dioxide  can  be  driven  off  the  raw  mate- 
rial and  still  Portland  cement  clinker  will  not  be  the  result.  For 
this  it  is  necessary  that  the  lime  combine  with  the  silica  and 
the  alumina,  and  in  order  for  this  combination  to  take  place  it  is 
necessary  for  the  material  to  be  heated  to  a  considerably  higher 
temperature  than  that  necessary  to  drive  off  carbon  dioxide.  If 
a  small  sample  of  raw  material  is  heated  to  a  constant  weight 


BURNING-KILNS    AND     PROCESS 


181 


over  an  ordinary  laboratory  blast  lamp,  very  little,  if  any, 
clinkering  will  take  place,  except,  perhaps,  on  the  under  side  of 
the  sample  next  to  the  crucible,  yet  all  the  carbon  dioxide  will 
have  been  driven  off.  The  various  opinions  as  to  the  constitu- 


,6-0  Dia. 


Stall*  Sta.15  Sta.fo  Stft.13  £ 
"•Su   4  Ft.    8  Ft.    12|Ft. 


Feed  End 


70 


50 


40 


20 


10 


-Ignition  I 


.12  Sta.llSb 
'Ft.  20 'Ft. 


.10   Sta.9    Sta.8   Sta.7 


Sta.6    Sta.5    Sta.4  Stn.3    Sta.2 


40  Ft.  44  Ft.  m  Ft.  52  Ft. 


60-0  Total  Length  of  Kiln- 


Discharge  End 


Fig.  52.— Chemical  changes  in  a  6  ft.  X  60  ft.  rotary  kiln. 

tion  of  Portland  cement  clinker  have  been  fully  detailed  in  Chap- 
ter II  on  the  chemical  composition  of  Portland  cement,  and  it  is 
unnecessary  here  to  repeat  them.  W.  B.  Newberry's  experiment 
on  the  various  stages  of  burning  given  below,  and  E.  D.  Camp- 
bell's researches  as  to  clinkering  temperatures,  also  outlined 
further  on,  have  done  something  to  advance  our  knowledge  of 
cement  burning. 


1 82  PORTLAND  CEMENT 

Wm.  B.  Newberry's  experiment1  is  of  great  interest  as  tend- 
ing to  throw  some  light  on  the  question  of  what  takes  place  dur- 
ing the  passage  of  the  raw  material  through  the  kiln. 

During  a  temporary  shutdown  of  one  of  the  rotaries  at  the 
Dexter  Portland  Cement  Co.,  at  Nazareth,  Pa.,  the  kiln  was  al- 
lowed to  cool  down  without  being  emptied  and  samples  of  the 
charge  were  then  taken  from  every  four  feet  throughout  the 
length  of  the  kiln. 

After  careful  examination  these  samples  were  analyzed,  the 
results  showing  the  changes  which  take  place  in  the  composition 
at  successive  stages  of  the  burning.  The  raw  material  used  was 
cement-rock  without  the  addition  of  any  other  material.  The 
first  sample  was  of  unburned  raw  material  taken  at  the  point  of 
entering  the  kiln  and  the  last  (No.  14)  was  the  finished  clinker 
within  four  feet  of  the  discharge  at  the  lower  end.  Fig.  52 
shows  graphically  the  chemical  charges  which  occurred  in  this 
experiment. 

The  physical  change  from  raw  stone  to  clinker  is  shown  by 
the  characteristics  of  the  different  samples  given  below : 

"  Nos.  i,  2  and  3,  blue  gray  powder,  changing  to  buff  between  3  and  4. 

"  Nos.  4,  5  and  6,  yellowish  buff  powder,  commencing  in  6  to  ball  up  into  small 
lumps. 

"  Nos.  7,  8,  9  and  10,  yellow  to  brown  balls  like  marbles  ;  soft,  easily  crushed  in  the 
fingers,  becoming  darker  and  harder  toward  10. 

"  No.  ii,  lumps  quite  hard  and  brown,  traces  of  sintering  on  surface,  softer  inside. 

"No.  12,  lumps  brown  and  partly  sintered,  beginning  to  lose  regular  rounded  forms 
hard. 

"  No.  13,  larger  lumps,  irregular  and  rough,  almost  black.  Very  noticeable  difference 
between  12  and  13,  latter  is  like  brownish  clinker  and  is  burnt  throughout. 

"  No.  14,  smaller  and  more  rounded  lumps,  black,  has  all  the  appearance  of  finished 
clinker,  in  fact,  no  further  change  is  seen  as  it  leaves  the  rotary. 

Soper  in  a  paper  read  before  the  American  Society  of  Mechani- 
cal Engineers,  Nov.  9,  1910,  gives  the  results  of  a  similar  test 
of  a  6  X  160  ft.  rotary  kiln.  His  results  are  plotted  in  Fig.  53. 
A  comparison  of  these  two  diagrams  (Figs.  52  and  53)  is  in- 
teresting as  explaining  the  economy  of  the  long  kiln.  If  the 
dips  in  the  lines  of  the  various  compounds  are  taken  out,  which 
should  be  done,  as  these  dips  are  merely  due  to  unavoidable 
analytical  and  experimental  errors,  and  the  lines  are  plotted  to 
smooth  curves,  it  will  be  seen,  that  in  the  long  kilns,  practically 
no  chemical  change  takes  place  for  the  first  80  ft.  other  than  the 
driving  off  of  the  water.  Up  to  this  point  practically  all  of  the 

1  Cement  and  Engineering  News,  Vol.  XII,  No.  5. 


|S 


0s! 


ii 


ii 


184  PORTLAND  CEMENT 

heat  taken  up  by  the  materials  has  been  employed  in  merely 
heating  them  up  to  the  temperature  at  which  dissociation  of  the 
carbon  dioxide  begins  (about  1,000°  F.).  From  this  point  to  a 
point  130  ft.  from  the  entrance  of  the  kiln  all  the  heat  absorbed 
by  the  material  is  utilized  for  two  purposes,  viz :  partly  for  the 
dissociation  of  the  carbon  dioxide  and  partly  to  heat  the  material 
up  to  the  temperature  necessary  to  clinker  (about  2,200° -2,500° 
F.)  while  in  the  last  20  ft.  of  the  kiln  the  clinkering  itself  takes 
place.  This  is  supposed  to  require  no  heat  and  to  take  place  as 
soon  as  the  critical  temperature  of  combination  is  reached.  It 
is  supposed  and  has  been  seemingly  experimentally  demonstrated 
that  heat  is  given  off  in  clinkering.  With  the  long  kiln  (160  ft.), 
therefore,  it  will  be  seen  that  over  half  the  kiln  is  utilized  to 
heat  the  material  up  to  the  point  at  which  the  dissociation  of  the 
carbon  dioxide  begins,  while  with  the  short  (60  ft.)  kiln  only 
about  one  quarter  or  sixteen  feet  of  the  length  is  so  used,  con- 
sequently this  1 6  ft.  must  be  very  much  hotter  in  order  to  do 
the  work  of  the  90  ft.  in  the  longer  kiln,  and  the  gases  must 
therefore  here  leave  the  kiln  at  a  much  higher  temperature. 
The  function  of  the  extra  length  is  therefore  to  use  the  heat 
of  the  gases  in  warming  the  incoming  material. 

Temperature  of  Burning. 

Campbell  made  numerous  experiments  in  burning  mixtures  of 
marl  and  clay  in  varying  proportions  in  a  small  rotary  kiln1 
fitted  with  a  Le  Chatelier  pyrometer  and  observing  the  properties 
of  clinker  formed  at  various  temperatures.  From  these  experi- 
ments he  fixed  the  temperature,  necessary  to  properly  burn  most 
commercial  cements  at  1550°  C.  or  2822°  F.,  while  high  limed 
cements  would  require  an  even  greater  temperature.  For  exam- 
ple;2 he  found  a  mixture  of  clay  and  marl  in  which  the  ratio  of 
the  silicates  (SiO2  -f  A12O3  +  Fe2O3)  was  to  the  lime  (CaO) 
as  100  : 228.8,  and  which  gave  a  clinker  containing  62.64  per 
cent,  lime,  to  require  a  temperature  of  1549°  C.  for  proper  burn- 
ing, while  a  mixture  of  the  same  clay  and  marl  in  which  the  sili- 
cate-lime ratio  was  100  : 240.8  and  which  gave  a  clinker  analyz- 

iy.  Am.  Chem.  Soc.,  XXIV,  248. 
»/.  Am.  Chem.  Soc.,  XXIV,  969. 


BURNING-KILNS    AND    PROCESS  185 

ing  63.83  required  a  temperature  of  1593°  C.  A  third  mixture  ot 
these  materials  having  a  silicate-lime  ratio  of  100:  266.4  and  giv- 
ing a  clinker  analyzing  66.12  per  cent,  lime  failed  to  burn  per- 
fectly even  at  1625°  C. 

This,  of  course,  Corroborates  the  experience  of  every  cement 
chemist,  that  the  higher  lime,  other  things  being  equal,  the 
higher  temperature  is  needed  to  burn  it. 

In  the  same  series  Campbell  also  found  that  the  mixture  of 
clay  and  marl  with  the  silicate-lime  ratio  of  100:  228.8,  which 
required  a  temperature  of  1549°  C.  for  proper  burning  could  be 
burned  at  a  temperature  of  1478°  C.  by  revolving  the  kiln  more 
slowly.  This  again  corroborates  the  experience  of  manufactur- 
ers, that  a  longer  time  in  the  kiln  would  do  the  same  work  as  a 
much  higher  temperature. 

In  a  second  experiment,1  Campbell  and  Ball  investigated  the 
influence  of  fine  grinding  of  the  raw  materials  on  the  clinkering 
of  cement.  A  mixture  of  cement-rock  from  the  Lehigh  District, 
as  ground  ready  for  the  kiln  by  a  prominent  mill  of  this  region, 
was  subjected  to  a  sieve  test  and  found  to  run  72.4  per  cent, 
through  a  2oo-mesh  sieve  and  85.6  per  cent,  through  a  loo-mesh 
sieve.  This  mixture  could  not  be  thoroughly  burned  even  at 
1612°  C.,  but  when  reground  so  that  98  per  cent,  of  it  passed  a 
2oo-mesh  sieve  proper,  burning  was  accomplished  at  a  tempera- 
ture of  1475°  C-  or  137°  C.  less.  This  experiment  is  valuable  as 
showing  the  importance  of  fine  grinding  in  fuel  economy.  While 
it  would  probably  be  impracticable  to  grind  hard  raw  materials  to 
a  fineness  of  98  per  cent,  through  a  2OO-mesh  sieve,  it  is  practica- 
ble and  indeed  is  usual  to  grind  more  than  85  per  cent,  through  a 
loo-mesh  sieve. 

One  objection  to  Campbell's  experiments  is  that  he  apparently 
took  no  account  of  time  in  the  kiln,  which  is  an  important  factor 
in  the  clinkering  of  cement.  Unquestionably  the  longer  the  mate- 
rial is  in  the  kiln  the  lower  the  temperature  at  which  clinkering 
takes  place.  The  author's  tests  show  that  the  long  (100  ft.  and 
over)  kilns  work  at  a  lower  temperature  than  the  60  ft.  kilns,  and 
this  is  no  doubt  one  reason  why  the  long  kilns  are  the  more 

i/.  Am.  Chem.  Soc.,  XXV,  1103. 


i86 


PORTLAND  CEMENT 


economical  of  the  two.  The  temperatures  of  most  125  ft.  kilns 
observed  by  the  author  are  fully  100°  C.  lower  than  those  em- 
ployed in  the  60  ft.  kilns.  The  temperatures  in  the  clinkering 
zone  of  a  125  ft.  kiln  usually  range  between  1,350  and  1,450°  C. 
Soper1  measured  the  temperature  at  various  points  in  a  kiln 
7  X  100  ft.  by  means  of  a  Le  Chatelier  pyrometer  by  inserting  the 


*fe- 

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a.4               St 
91°               15 
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gth  of  Kiln 
a.3              Stz 
81°                20 
f-0"                66 

r~  3 

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a.8               St 
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a.5              St 
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i.2               St 

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81°          1271° 
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a  Teruperatu 
i.3              St 
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res  of  Gases 
i.2              St 
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i.i             Stt 

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Curve-2-Maximum  Temperatures  of  Materials 

Calculated  from  Gas  Temperatures 
Note:-  Temp's  at  Sta's  B,l,  12  Actually  Observed 

Fig.  54.— Temperature  of  gases  and  materials  in  a  6  ft.,  7  ft.  X  100  ft.  rotary 
kiln,  wet  process. 

porcelain  tubes  containing  the  elements  through  holes  previously 

1  Paper  read  before  Western  Society  of  Engineers,  Nov.  15,  1905. 


BURNING-KILNS    AND     PROCESS  l8/ 

drilled  through  the  kiln  shell  and  fire  brick  lining.  This  kiln  was 
working  upon  wet  materials.  Fig.  54  shows  the  temperature  of 
the  gases  at  various  points  in  the  kiln  as  ascertained  in  this  test. 

While  there  is  no  definite  information  to  that  effect  it  is  gen- 
erally accepted  as  a  fact  that  the  presence  of  alkalies  lower  the 
temperature  at  which  clinkering  takes  place.  In  a  small  furnace 
which  the  writer  had  he  could  never  quite  get  the  temperature  up 
to  the  point  for  a  thorough  burning  of  the  Lehigh  cement-rock 
limestone  mixtures,  but  if  the  small  cubes  of  powdered  mate- 
rial were  made  up  with  water  containing  enough  sodium  carbon- 
ate to  make  the  mixture  analyze  about  1.5  per  cent,  soda,  the 
clinkering  could  easily  be  accomplished. 

Iron  always  plays  an  important  part  in  aiding  the  clinkering. 
The  white  Portland  cements  at  present  on  the  market  are  all 
hard  to  burn.  Fluorspar  or  calcium  fluoride,  CaF2,  has  also  the 
effect  of  lowering  the  clinkering  temperature  and  has  been  used, 
commercially,  for  that  purpose,  I  believe. 

Degree  of  Burning. 

Properly  burned  Portland  cement  clinker  is  greenish  black  in 
color,  of  a  vitreous  luster  and  usually  when  just  cooled  sparkles 
with  little  bright  glistening  specks.  It  forms  in  lumps  from  the 
size  of  a  walnut  down,  with  here  and  there  a  larger  lump.  Un- 
derburned  clinker,  whether  this  is  due  to  a  low  temperature  in 
the  kilns  or  an  overlimed,  mixture  lacks  the  vitreous  luster  and 
the  glistening  specks.  The  failure  to  sparkle,  however,  is  not  nec- 
essarily characteristic  of  underburned  clinker,  though  the  sparkle 
itself  is  never  seen  in  underburned  clinker,  as  the  rate  of  cooling 
etc.,  effects  this  somewhat.  If  much  underburned,  the  clinker  is 
brown,  or  has  soft  brown  or  yellow  centers.  Low  limed  clinker 
unless  very  carefully  burned,  usually  has  brown  centers  also,  but 
is  hard  and  glassy.  The  two  should  not  be  mistaken ;  the  clinker 
with  soft  brown  centers  is  underburned  that  with  hard  brown 
centers  is  underlimed. 

Overburned  clinker  shows  the  same  characteristic  as  under- 
limed, — the  hard  brown  centers.  I  have  never  seen  that  the 
quality  of  cement  was  injured  any  by  everburning,  unless  the 


1 88  PORTLAND  CEMENT 

material  was  low  in  lime  when  the  resulting  cement  was  apt  to  be 
"quick-setting,"  but  the  proper  degree  of  sintering  is  far  enough 
to  carry  the  process  and  to  burn  any  harder  is  not  only  a  waste 
of  coal  for  burning,  but  also  for  grinding  since  the  hard  brown 
slag  like  clinker  is  very  hard  to  pulverize.  Properly  burned 
clinker  should  have  a  specific  gravity  of  at  least  3.15  and  when 
rapidly  pulverized  and  ignited  show  a  loss  of  under  i  per  cent. ; 
although  neither  of  these  tests  is  of  any  value  in  determining  the 
thoroughness  of  burning,  when  applied  to  ground  cement. 

Thermo-Chemistry  of  Burning. 

These  chemical  changes  or  reactions  taking  place  in  the  burn- 
ing of  Portland  cement  either  give  off  or  require  heat.  If  the 
former  they  are  exothermic,  if  the  latter  endothermic. 

The  exothermic  or  heat  generating  reactions  are  the  burning  of 
the  sulphur  and  carbon  (organic  matter)  of  the  raw  materials. 
The  endothermic  or  heat  absorbing  ones  are  the  decomposition 
of  the  calcium  and  magnesium  carbonates. 

The  combination  of  the  lime  with  the  silica  and  alumina  is  also 
thought  to  be  an  exothermic  reaction,  but  authorities  differ  on 
this  point. 

The  quantity  of  heat  generated  by  chemical  reaction  or  re- 
quired to  bring  it  about  is  usually  expressed  in  terms  of  one  of 
two  units.  These  are  the  British  Thermal  Unit,  usually  ab- 
breviated to  B.  t.  u.  and  the  Calorie  sometimes  abbreviated 
to  Cal.  The  British  thermal  unit  is  the  heat  required  to  raise 
the  temperature  of  one  pound  of  pure  water  through  one  degree 
Fahrenheit  at  or  near  39.1°  F.,  the  temperature  of  its  maximum 
density.  The  calorie  is  the  heat  necessary  to  raise  the  tempera- 
ture of  one  kilogram  of  water  from  4°  C.  to  5°  C.  A  calorie  is 
equivalent  to  3,968  B.  t.  u.,  and  a  B.  t.  u.  to  0.252  calorie.  The 
B.  t.  u.,  however,  produced  by  the  oxidation  or  combustion  of 
one  pound  of  a  substance  is  9/5  of  the  number  of  calories  which 
would  be  produced  by  one  kilogram  of  the  substance.  Hence, 
to  reduce  calories  per  kilogram  to  B.  t.  u.  per  pound  multiply 
by  9/5  while  to  change  B.  t.  u.  per  pound  to  Calories  per  kilo- 
gram multiply  by  5/9. 


BURNING-KILNS    AND    PROCESS  189 

The  British  thermal  unit  is  the  one  generally  used  by  engi- 
neers for  expressing  the  heating  value  of  fuel  while  the  calorie  is 
used  in  most  scientific  calculations. 

The  following  are  heat  values  of  the  reactions  mentioned 
above : 

B.  t.  u. 

i  pound  of  carbon  burned  to  CO2  gives  off 14,540 

i  pound  of  sulphur  burned  to  SO2  gives  off  - 4,050 

i  pound  of  CaCO3  decomposed  into  CO2  and  CaO  requires  784  l 
i  pound  of  MgCO:i  decomposed  into  CO2  and  MgO 

requires-- 384  l 

i  pound  of  CaO  uniting  with  SiO2  and  A12O3  gives  off. .  1064  l 
0.56  pound  of  CaO,  equivalent  to  i  pound  of  CaCO3 

uniting  with  SiO2  and  A12O3,  gives  off 596  l 

Calories 

i  kilogram  of  carbon  burned  to  CO2  gives  off 8.080 

i  kilogram  of  sulphur  burned  to  SO2  gives  off-  •  -  • 2,250 

i  kilogram  of  CaCO3  decomposed  into  CO2   and  CaO 

requires i 436  l 

i  kilogram  of  MgCO3  decomposed  into  CO2  and  MgO 

requires 213  l 

i  kilogram  of  CaO  uniting  with  SiO2  and  A12O3  gives  off  591  1 
0.56  kilogram  of  CaO,  equivalent  to  i  kilogram  of  CaCO3 

uniting  with  SiO2  and  A12O3  gives  off 33 1  l 

As  I  have  said  there  is  some  doubt  about  the  heat  given  off  by 
the  combination  of  the  lime  with  the  silicates,  and  this  point  needs 
investigation.  It  is  the  stumbling  block  to  our  calculating  the 
efficiency  of  the  rotary  kiln.  As  it  seems  probable  that  the  reac- 
tion does  give  off  some  heat,  though  the  amount  is  probably  very 
small,  we  can  arrive  at  the  maximum  heat  theoretically  required 
to  burn  a  barrel  of  cement,  or  rather  the  heat  from  outside 
sources  absorbed  by  the  chemical  reactions. 

As  we  have  said  heat  is  required  to  decompose  the  carbonates 
and  is  given  off  by  the  burning  of  the  carbon  and  the  sulphur  of 
the  mix.2  The  raw  material  of  the  Lehigh  District  contains  per 
100  pounds,  about 

1  Berthelot,  Thermochemie,  Vol.  II.     These  values  are  dubious. 

2  If  the  sulphur  of  the  mixture  is  present  as  sulphide,  it  burns,  giving  off  heat.    If 
present  as  sulphate,  heat  is  required  to  expell  it  (1890  B.  t.  u.  per  pound). 


I9O  PORTLAND 

Pounds 

Carbonate  of  lime 75  .o 

Carbonate  of  magnesia 4.0 

Carbon 0.8 

Sulphur 0.3 

Hence,  there  would  be  required  heat  as  follows : 

B.  t.  u.  B.  t.  u. 

To  decompose  75  Ibs.  of  CaCO3  =  75  X  784 58,800 

To  decompose  4  Ibs.  of  MgCO3  —    4  X  384 i,536        60,336 

There  would  be  given  off: 

By  burning  of  0.3  Ibs.  of  sulphur  =  0.3  X4,O5°*-I»2I5 

By  burning  of  0.8  Ibs.  of  carbon  0.8  X  14,540-  .11,632        12,847 


Balance  to  be  supplied  by  fuel 47,489 

Since  I  barrel  of  cement  requires  about  600  Ibs.  of  dry  material: 
it  would  require  47,489  X  6  B.  t.  u.,  or  reckoning  I  Ib.  of  Fair- 
mont gas  slack  at  14,000  B.  t.  u.,  I  barrel  of  cement  would  re- 
quire    or  20.55  Ibs.  of  coal. 

14,000 

.  If  we  consider,  however,  that  heat  is  given  off  by  the  combina- 
tion of  the  lime  with  the  silicates,  then  this  heat  would  amount  to 
75  X  596  =  44,700  B.  t.  u.  Subtracting  this  from  47,489  would 

leave  only  2,789  B.  t.  u.  to  be  supplied  by  the  coal  or  — — 

14,000 

=  1.2  Ibs.  of  coal  per  barrel.  This  latter  figure  seems  hardly 
probable. 

Of  course,  the  figure  20.35  ^s-  °f  coal  Per  barrel  is  an  ideal 
one,  and  in  order  to  realize  it  in  practice  we  would  have  to  re- 
cover all  the  heat  not  actually  utilized  in  the  chemical  reaction. 
We  would  have  to  cut  off  all  radiation  from  the  kiln,  the  clinker 
and  flue  gases  would  have  to  leave  the  kiln  at  the  temperature  of 
the  air,  and  we  would  have  to  condense  the  water  evaporated 
from  the  mix  and  recover  the  heat  units  expended  upon  it. 

Of  course,  it  is  impossible  to  do  this  economically.  There  will 
always  be  some  loss  by  radiation,  and  the  water  must  leave  the 
kiln  at  a  temperature  above  its  boiling-point.  We  must  also  have 
sufficient  difference  between  the  temperatures  of  the  waste  gases 
and  the  outside  air  to  produce  natural  draft.  Table  XVIII  shows 


BURNING-KILNS    AND    PROCESS  IQI 

the  various  constants  necessary  to  calculate  the  heat  carried  off 
by  the  kiln  gases  and  the  clinker. 

TABLE  XV.— CONSTANTS1,  ETC.,  FOR  USE  IN  CALCULATING  THE  HEAT 
LOSSES  OF  THE  ROTARY  KILN 

Pounds 
Weight  of  air  necessary  to  burn  one  pound  of — 

Carbon  (to  CO2) 11.7 

Hydrogen  (to  H2O)  34.8 

Sulphur  (to  SO2) 4-4 

Weight  of  products  of  combustion  from  one  pound  of — 

Carbon CO2  =  3.66  Ibs.     N  ==    8.94  Ibs. 

Hydrogen H2O  =  9.00  Ibs.     N  =   26.8  Ibs. 

Sulphur SO3  =  2.00  Ibs.     N=    3.35  Ibs. 

B.  t.  u. 

Heat  required  to  evaporate  i  Ib.  of  water 996 

Specific  heat  of  products  of  combustion  of  I  Ib.  of  gas 

slack  coal 0.250 

Specific  heat  carbon  dioxide 0.234 

Specific  heat  carbon   monoxide 0.245 

Specific  heat  nitrogen o.  244 

Specific  heat  air 0.238 

Specific  heat  steam 0.480 

Specific  heat  water i  .000 

Specific  heat  clinker 0.246 

Below  is  an  analysis  of  Fairmont  gas  slack  coal  (such  as  is  used 
in  the  Lehigh  District)  made  by  the  writer: 

Water  (no°C.) 1.9 

Carbon 74.9 

Hydrogen 4.8 

Oxygen 8.6 

Nitrogen 1.4 

Sulphur o.  7 

Ash 7.7 

IOO.O 

Neglecting  the  sulphur  which  is  present  only  in  very  small 
amount  the  combustible  elements  in  100  Ibs.  of  this  coal  are  74.9 
Ibs.  of  carbon  and  4.8  ibs.  of  hydrogen.  Of  this  hydrogen,  how- 

Q     £ 

ever,  — — -  Ibs.  will  be  needed  for  the  oxygen  of  the  coal  itself, 
8 

1  These  constants  are  of  course  mere  approximations,  but  are  sufficiently  near  the 
truth  for  rapid  calculations  of  heat  losses. 


192  PORTLAND  CEMENT 

O      fi 

leaving  only  (4.8 '—-  =  4.8  —  i.i  —  3.7)  to  require  outside 

8 

oxygen;  hence,  to  burn  100  Ibs.  of  this  coal  will  require 

For  the  carbon 74.9  X  n.6  =  869  Ibs.  air 

For  the  hydrogen 3-7  X  34-8  =  129  Ibs.  air 

Total  for  100  Ibs.  coal . =  998  Ibs.  air 

Total  for  i  Ib.  coal =  10.0  Ibs.  air 

The  products  of  combustion  from  100  Ibs.  coal  would  of 
course  weigh  998  Ibs.  +  combustible  and  volatile  part  of  the 
coal  or  998  +  (100  —  ash). 

Therefore,  products  of  combustion  from  100  Ibs.  of  coal  would 
weigh  998  +  (100  —  77)-=  1090  and  products  of  combustion 
from  one  pound  of  coal  10.9  Ibs. 

Now  neglecting  the  unimportant  elements : — 
The  combustion  of  74.8  Ibs.  of  car- 
bon will  produce- 74- 8  X  3. 66  =  274  Ibs.  of  CO2 

And 74.8  X  8.94  =  669  Ibs.  of  N. 

The  combustion  of  3.7  Ibs.    of  hy- 
drogen will  produce 3.7  X    9    =33lbs.  ofH2O 

And 3-7  X  26.8  =  99  Ibs.  of  N. 

Now  there  are  1.9  Ibs.  of  water  from  the  moisture  of  the  coal 
and  8.6  -f-  — —  =  9.7  Ibs.  from  the  oxygen  of  the  coal,  hence 

o 

there  will  be  in  the  products  of  combustion  from  100  Ibs.  of  coal 
768  Ibs.  of  nitrogen,  274  Ibs.  of  carbon  dioxide,  and  44.6  Ibs.  of 
water. 

Hence,  the  mean  specific  heat  of  the  gases  will  then  be: — 

Nitrogen 768  X  0.244  =  187.4 

Carbon  dioxide 274  X  0-234  =    64.  i 

Water  (steam) 45X0.48    =    21.6 


1,087  273.1 

27  "^   I 

Mean  specific  heat  =  — — 0.251. 

1,087 

This  figure  may  be  taken  as  fairly  representative  of  the  specific 
heat  of  the  products  of  combustion  from  gas  slack  coal.  It  is  of 
course  not  a  very  exact  figure  because  the  specific  heat  of  gases 
increases  slightly  with  their  temperature.  It  is  probably  exact 


BURNING-KILNS    AND    PROCESS 


193 


enough  for  ordinary  purposes,  however,  since  in  most  calcula- 
tions of  this  sort  so  much  is  assumed  that  very  exact  figures 
are  merely  a  waste  of  mathematics. 

Numerous  tests  of  the  waste  gases  of  the  rotary  kiln  working 
on  dry  material  under  normal  conditions  show  a  temperature  at 
the  mouth  of  the  kiln  from  500°  F.  to  2,000°  F.  Analysis  of 
these  gases  also  show  some  excess  of  air,  not  so  much  as  some- 
times stated,  but  still  from  15  to  30  per  cent.  From  his  exper- 
ience, the  writer  would  say  that  the  average  temperature  of  the 
flue  gases  from  an  8  X  I25  foot  kiln,  taken  from  the  kiln  mouth 
before  being  diluted  with  the  air  leaking  into  the  stack,  is  at  least 
900°  F.,  and  that  the  excess  air  is  20  per  cent,  of  that  actually 
required.  The  average  coal  consumed  in  this  size  kiln  is  80  Ibs. 
per  barrel  (not  counting  coal  used  to  heat  up  kiln  after  patching, 
etc.,)  and  the  average  weight  of  CO2  driven  off  per  barrel  is 
200  Ibs. 

Then  using  data,  in  Table  XVIII,  the  heat  lost  up  the  stack  is : 


B.  t.  u. 

per  degree 

above  temp. 

of  atmosphere 

In  products  of  combustion  of  So  Ibs.  of  coal 

=  loo  X  10.9  X  0.251  = 218.9 

In     CO.2    driven    off    from    raw     material 

=  200  X  0-234  = 46.8 

In       excess      air      used      to      burn      coal 

=  80  X  10.0  X  0.20  X    0.238 39-1 

304.8 

If  the  outside  air  is  50°  F.  the  gases  would 
contain  304.8  X  (900  —  50)  = 

If  raw  material  contains  2^»  mois- 
ture, to  raise  600  X  0.02  or  12  Ibs. 
of  water  from  50°  to  212°  F.  re- 
quires 12  X  (212  —  50)  = i,944 

To  evaporate  12  Ibs.  of  water  re- 
quires 12  X  966  = n,592 

To  raise  12  Ibs.  steam  from  212  to 

900  =   (900  —  212)  X   12  X  0.48.       3,963 

Total  heat  lost  in  waste  gases 

13 


B.  t.  u. 
in  gases 


259,080 


17,499 


276,579 


194  PORTLAND 

Since  I  Ib.  coal  =  14,000  B.  t.  u.,  heat  lost  up  stack  is  equivalent  to 
276, 579 -^-  14,000  —  19.7  pounds  of  coal. 

Also  380  Ibs.  of  clinker  at  2160°  F.  (usual  temperature  of  clinker  leaving 
the  kiln)  will  contain  380  X  (2,160—50)  X  0.246=  197,243  B.  t.  u.  or 

^7>     3  =  14.1  pounds  of  coal. 
14,000 

Total  heat  carried  off  by  the  waste  gases  and  clinker  is  therefore  equiva- 
lent to  33.8  pounds  of  coal  or  42.25  per  cent,  of  fuel. 

If  the  loses  in  the  clinker  and  gas  are  equivalent  to  33.8  Ibs. 
of  coal  and  20.35  ^>s.  are  needed  for  chemical  reactions,  the 
radiation  losses  are  equivalent  to  80  —  (33-8  +  20.35)  or  26 
Ibs.  of  coal,  equivalent  to  32.5  per  cent,  of  the  heat  supplied. 

The  above  conditions  are  not  exaggerated,  but  are  a  fair  ex- 
ample of  conditions  as  they  are  usually  met  with  in  burning  dry 
material  in  a  kiln  of  this  size. 

It  is  interesting  to  note  to  what  figure  ideal  practice  would  re- 
duce the  coal  consumption.  If  the  kiln  gases  are  reduced  to  450° 
F.,  it  will  be  no  better  than  ordinary  boiler  practice  in  many 
power  plants.  The  excess  air  is  now  as  low  as  20  per  cent. 
It  would  also  be  possible  to  reduce  the  temperature  of  the  clinker 
to  150°  F.,  or  even  lower.  Under  these  conditions  let  X  =  coal 
consumed : 

Then  as  before  heat  carried  off  : 

B.  t.  u. 

per  degree 

above  temperature 

of  atmosphere 

In  products  of  combustion  X  X  IO-9  X  0-251  = 2.74  X 

In  CO2  from  raw  material 46.8 

In  excess  air  X  X  10.0  X  °-2°  X  0-238 0.48  X 

Total  =  (2.74  X  +  0.48  X  -f  46.8)  400  =  (3.22  X  4- 

46.8)  400  = 1,288  X  4-  18,720 

To  raise  12  Ibs.  water  from  50-212°  F.  and  evaporate  same 

=  v 13,536 

To  raise  12  Ibs.  steam  from  212-450  =  (450  —  212  X  12  X 
0.48 1,371 

Total  to  evaporate  water 14,907  B.  t.  u. 

Total  heat  in  products  of  combustion,   1,288  X  -f  18,720 
4-  14,907  = 1.288  X  4-  33,527  B.  t.  u. 

Now  the  clinker  will  carry  off  at  150°  F.  380  X  (150 — 50) 
X  0.246  =  9,348  B.  t.  u. 

The   chemical  reaction  will  require  as  calculated  47,489 
X  6  =  284,  934  B.  t.  u. 

Or  the  whole  process  will  require  1,288  X  -\-  33,627  -\- 
9,348  -I-  284,934  B.  t.  u. 

Or  since  coal  gives  off  14,000  B.  t.  u.   we  have  the  equa- 
tion. 1,288  X -{-  33.627  -f  9,348  4-  284,934  =  14,000  X. 

Or  327,909  =  12,712  X. 

X=  25.8  pounds. 


BURNING-KILNS    AND    PROCESS  195 

Therefore,  we  should  hope  to  burn  cement  ultimately  with  30 
Ibs.  of  coal  per  barrel.  Of  course  the  value  of  coal  depends 
largely  upon  the  heat  units  is  contains  and  40  per  cent,  more  of 
a  coal  giving  off  only  10,000  heat  units  will  be  required. 

Excess  Air   Used   in  Burning. 

The  excess  of  air  admitted  to  the  kiln  over  and  above  that  re- 
quired to  consume  the  coal  has  been  variously  stated  at  from 
loo  to  150  per  cent,  above  the  theoretical  quantity.  From  the  re- 
sult of  many  analyses  made  by  myself  and  assistants  I  am  confi- 
dent that  this  does  not  represent  normal  conditions.  If  the 
sample  is  taken  from  the  kiln  stack  a  large  quantity  of  air,  which 
has  leaked  in  through  the  annular  opening  between  the  kiln 
and  the  brick-work  of  the  flue  is  sure  to  be  present,  and  conse- 
quently make  the  excess  air  appear  much  greater  than  it  really 
is.  The  gas  samples  should  be  taken  from  the  inside  of  the 
mouth  of  the  kiln  so  that  there  is  no  air  mixed  with  it  which 
does  not  pass  through  the  kiln.  Below  are  given  some  average 
analyses  of  waste  gases  from  kilns  working  under  various  con- 
ditions. 

1.  Average  of  all  samples  taken  when  the  kiln  was  working 
normally.     No  flame  or  black  smoke  issuing  from  the  kiln  stack 
but  only  a  thin  white  or  reddish  vapor. 

Carbon  dioxide 27.4 

Carbon  monoxide 0.3 

Oxygen 2.7 

Nitrogen. 69.6 

100.0 

2.  Average  of  all  samples  taken  when  the  kiln  stacks  were 
smoking. 

Carbon  dioxide 19.2 

Carbon  monoxide 1.2 

Oxygen 3.4 

Nitrogen 76. 2 

100.  o 


196  PORTLAND 

3.  Average  of  all  samples  taken  when  kiln  stacks  were  flaming: 

Carbon  dioxide 14.2 

Carbon  monoxide  .  i 5.8 

Oxygen....   i.i 

Nitrogen 78.9 

100.  o 

The  nitrogen  in  the  gases  represents  the  air  admitted  for  com- 
bustion as  practically  all  of  it  is  from  either  the  excess  air  or  the 
air  actually  used  to  burn  the  coal.  A  small  part  of  the  nitrogen 
conies  from  the  coal,  however,  but  for  practical  calculations  the 
nitrogen  may  be  considered  as  all  coming  from  the  air.  The  ex- 
cess air  is  shown  by  the  oxygen.  If  we  calculate  the  nitrogen 
equivalent  to  this  oxygen  by  multiplying  the  percentage  of  the 
latter  by  3.78,  the  result  will  be  the  nitrogen  carried  in  by  the 
excess  air  and  this  nitrogen  subtracted  from  the  total  percentage 
of  nitrogen  found  by  the  analysis  will  give  the  nitrogen  belong- 
ing to  the  air  needed  to  support  combustion,  from  which  data 
the  excess  can  be  calculated.  For  example,  to  find  excess  air 
in  sample: 

Analysis  No.  I. 

Per  cent. 

Total  nitrogen 69.6 

Nitrogen  in  excess  air  2.7  X  3-78 10.2 

Nitrogen  in  necessary  air 59.4 

Ratio :  59.4  :  69.4  :  :  100  :  x 

x  =  117. 
Excess  =  17%  of  air  necessary  to  combustion. 

The  above  calculation  is  not  strictly  accurate  for  a  number  of 
reasons,  but  for  practical  use.  it  answers  the  purpose  as  well 
since  we  never  know  in  mill  practice  under  present  conditions 
exactly  how  much  coal  we  are  burning,  or  how  much  carbon 
dioxide  is  being  driven  off  at  a  given  time  from  the  raw  mate- 
rial. 

Of  the  air  admitted  to  the  kiln  for  combustion,  between  20  and 
30  per  cent,  is  blown  in  with  coal ;  the  rest  enters  between  the 
hood  and  the  kiln  and  where  the  clinker  drops  out,  and  is  drawn 
in  by  the  draft  of  the  kiln. 


BURNING-KILNS    AND    PROCESS  IQ7 

Utilisation  of  Waste  Heat. 

Many  ways  have  been  proposed  for  saving  the  waste  heat  from 
the  rotary  kiln,  both  in  the  flue  gases  and  the  clinker. 

Robert  F.  Wentz  and  Lathbury  and  Spackman  both  patented 
clinker  cooling  devices  on  the  principle  of  blowing  air  through 
the  clinker  and  using  the  same  for  combustion  of  the  coal,  and 
each  firm  has  installed  their  system  in  the  mills  which  they  de- 
signed. Rotary  coolers  are  also  in  use  in  a  large  number  of 
works,  but  as  we  have  said  many  mills  still  use  the  large 
upright  coolers  mentioned  in  the  section  on  cooling  the  clinkers 
and  no  attempt  is  made  to  save  the  heat  of  the  clinker  in  spite  of 
the  fact  that  the  heat  in  the  clinker  represents  that  from  the  com- 
bustion of  14  Ibs.  of  coal.  There  should  be  no  mechanical  trouble 
about  designing  a  cooler  to  economize  this  heat,  and  yet  cool  the 
clinker.  In  some  of  the  regenerative  systems  the  writer  believes 
failure  to  have  resulted  simply  from  the  fact  that  the  designers 
did  not  realize  that  one  cubic  foot  of  air  at  600°  F.  would  not 
burn  as  much  coal  as  one  cubic  foot  of  air  at  60°  F.,  but  only 
about  half  as  much,  and  consequent  use  of  too  small  a  fan  to 
draw  the  air  through  the  cooler.  The  use  of  the  heat  of  the 
clinker  to  heat  the  water  for  the  boilers  should  also  prove  an 
easy  problem.  The  rotary  cooler  as  designed  to  save  the  heat 
in  the  clinker  is  described  in  Chapter  XII. 

In  the  early  days  of  the  rotary  kiln  Giron,  Nivarro,  Hurry 
and  others  patented  devices  for  utilizing  the  heat  of  the  waste 
gases. 

At  the  present  time  three  methods  are  being  employed  for 
the  saving  of  the  heat  in  the  kiln  gases. 

(i).  Lengthening  the  kiln,  thereby  giving  greater  time  for  the 
material  to  absorb  the  heat  of  the  kiln  gases. 

(2).  Passing  the  gases  of  the  ordinary  short  kiln  through  an 
upright  boiler  and  then  through  an  economizer. 

(3).  Utilizing  some  of  the  heat  in  the  gases  for  drying  the 
raw  materials. 

Thomas  A.  Edison  was  the  first  person  in  this  country  to  at- 
tempt a  kiln  longer  than  80  ft.,  those  at  his  plant  at  Stewartsville 
being  150  feet  long. 


198  PORTLAND  CEMENT 

These  kilns  were-put  in  operation  in  the  fall  of  1903  and  proved 
entirely  practical  and  effected  the  economy  in  fuel  which  Edison 
had  promised  they  would  do.  His  experiment  was  watched 
with  great  interest,  and,  as  soon  as  the  success  of  these  longer 
kilns  was  known,  several  of  the  mills  then  under  construction 
lengthened  their  kilns  to  80  feet.  This  plan  has  since  been  tried 
by  most  of  the  older  mills  who  extended  their  kilns  to  100  or 
more  feet.  All  of  the  mills  built  since  this  time  have  been  in- 
stalled 100  and  125-foot  kilns. 

The  attempt  to  utilize  the  heat  of  the  kiln  gases  under  boilers 
was  first  made,  I  believe,  at  the  plant  of  the  Nazareth  Portland 
Cement  Co.,  but  after  encountering  many  difficulties,  the  plan 
was  abandoned  and  the  boilers  taken  away.  Prof.  R.  C.  Car- 
penter, of  Cornell  University,  however,  tried  this  plan  at  the  plant 
of  the  Cayuga  Lake  Cement  Co.  and  also  at  the  plant  of  the 
Kosmos  Portland  Cement  Co.  where  it  seems  to  have  been  suc- 
cessful as  it  is  still  in  use  at  both  plants. 

The  first  of  these  concerns  has  a  small  plant  located  on  the 
shores  of  Cayuga  Lake,  about  six  miles  north  of  Ithaca,  N.  Y. 
In  this  plant  one  boiler,  of  the  vertical  water-tube  type,  as 
built  by  the  Wickes  Bros.  Mfg.  Co.,  and  of  3,000  square  feet  of 
water  heating  surface,  was  installed  for  each  two  kilns  of  the 
plant.  After  two  kilns,  composing  one-half  of  the  plant,  had 
been  in  operation  about  two  months,  a  test  was  made  to  determine 
the  economy  of  the  plant  and  also  the  amount  of  steam  obtained 
from  the  waste  gases. 

Prof.  Carpenter1  gives  the  following  description  of  the  test  and 
its  results. 

At  the  time  of  the  test  two  kilns  only  were  in  operation  and 
the  waste  heat  from  these  kilns  passed  through  one  boiler;  the 
other  boiler  when  used  being  fired  by  hand  exclusively.  The  tests 
of  the  two  boilers  were  made  on  different  days.  The  test  showed 
that  boiler  No.  I,  which  received  trie  waste  gases,  developed  406.8 
B.  H.  P.,  of  which  it  was  calculated  that  264  B.  H.  P.  was  pro- 
duced by  the  waste  heat  from  the  two  kilns  and  the  remainder 
from  coal  burned  on  the  grate.  When  boiler  No.  2  was  tested, 

1  Sibley  Journal  of  Engineering,  March,  1904  ;  also  Concrete,  November,  1904. 


BURNING-KILNS    AND    PROCESS  199 

boiler  No.  I  received  the  heat  from  the  waste  gases  of  two  kilns 
and  no  heat  from  hand  firing,  and  during  this  time  a  measurement 
of  the  feed  water  indicated  that  the  heat  from  the  waste  gases  was 
sufficient  to  produce  254  B.  H.  P.,  which  roughly  checks  the  pre- 
ceding test. 

Practically  all  cement  manufacturers  realize  the  great  loss  of 
heat  due  to  the  high  temperature  of  the  kiln  gases,  and  it  is  only  a 
question  of  time  until  all  plants  will  have  adopted  some  method 
of  saving  this  waste  heat.  The  long  kiln  seems  to  be  the  favorite 
method  at  present  adopted  by  the  newer  mills,  and  many  of  the 
old  ones  are  lengthening  their  kilns  from  125  to  150  feet.  While 
the  long  kiln  will  effect  some  economy  they  will  still  be  quite 
wasteful.  The  difficulty  that  has  kept  the  cement  manufacturer 
from  making  use  of  the  hot  blast  stoves  of  the  iron  manufacturer, 
namely,  the  large  quantity  of  dust  in  the  kiln  gases,  has  also 
interfered  somewhat  with  all  attempts  to  use  the  waste  gases 
under  boilers. 

From  some  observations  made  on  the  flue  gases  of  the  150- foot 
kilns  I  am  confident  that  in  order  to  reduce  the  kiln  gases  to 
400°  F.  the  temperature  obtained  in  good  boiler  practice,  it  would 
be  necessary  to  lengthen  these  kilns  to  at  least  250  feet  without 
increasing  the  diameter.  The  smaller  the  diameter  for  a  given 
length  the  greater  the  economy.  To  decrease  the  diameter  how- 
ever, is  to  decrease  the  capacity  because  it  decreases  the  coal  which 
can  be  burned. 


CHAPTER  VIII. 


BURNING    (CONTINUED)— FUEL  AND  PREPARATION  OF 
THE   SAME. 

As  we  have  said,  during  the  early  experiments  with  the  rotary 
kiln,  crude  oil  was  used  as  a  fuel.  The  growing  scarcity  and 
high  price  of  oil  led  to  the  abandonment  of  this  as  a  fuel,  ex- 
cept in  sections  where  oil  is  cheap  and  coal  high,  and  the  sub- 
stitution of  powdered  coal  in  its  place.  This  practice  became 
general  about  1899,  and  since  this  cheap,  form  of  fuel  was  in- 
troduced, no  new  plants  have  been  built  which  did  not  install 
rotary  kilns,  the  objection  to  them  previous  to  this  being  the 
high  cost  of  the  oil.  The  saving  effected  by  the  change  was 
considerable,  and  only  a  few  plants  in  this  country  use  crude 
oil,  and  these  are  situated  principally  near  oil  fields,  chiefly  in 
California  and  the  middle  west. 

Apparatus  for  Burning  Powdered  Coal. 

The  method  for  burning  the  powdered  coal  is  shown  in  Fig. 
55.  It  consists  of  an  injector  through  which  air  is  forced  by 
a  fan.  The  coal  is  conveyed  out  of  a  bin  by  a  screw  conveyor, 
falls  into  the  injector,  is  sucked  in  and  mingles  with  the  air  as 
it  passes  through  the  pipe  to  the  kiln.  The  injector  is  usually 
of  cast  iron,  the  pipe  leading  to  the  kiln  is  of  galvanized  iron 
and  terminates  in  a  nozzle  of  wrought  iron  pipe,  which  projects 
for  a  foot  or  more  through  the  hood  into  the  kiln.  The  screw 
conveyor  leading  from  the  bin  is  run  usually  by  a  line  shaft 
independent  of  the  kilns  and  usually  attached  to  the  fans  or 
the  motor  driving  the  fans.  The  connection  with  the  shaft 
is  made  either  by  some  form  of  speed  controller,  or  else  by  a 
stepped  pulley,  so  the  coal  feed  can  be  regulated.  The  air 
blown  in  is  constant  and  is  only  a  fraction  of  that  needed 
for  combustion,  usually  about  25  per  cent.  In  some  mills  air 
from  the  compressors  or  high  pressure  air  is  used,  and  in  others 
a  combination  of  the  two  is  sought.  When  high  pressure  air  is  used 


BURNING 


201 


this  is  supplied  by  an  air  compressor  at  about  60-80  Ibs.  pressure. 
From  7  to  10  per  cent,  of  the  quantity  theoretically  needed  for 
combustion  is  all  that  is  usually  supplied  at  this  pressure.  The 
main  object  in  any  event  is  merely  to  carry  the  coal  into  the 
kiln  and  to  get  a  good  mixture  of  coal  and  air. 


Fig-  55.— Method  of  burning  powdered  coal.     (B.  F.  Sturtevant  Co.) 

Fig.  56  shows  the  construction  of  an  injector  for  use  with 
low  pressure  air,  and  Fig.  57  one  for  use  with  high  pressure 
air.  It  is  of  course  desirable  to  intimately  mix  the  air  and 
coal  in  order  that  combustion  may  take  place  promptly.  Fig. 
58  shows  a  form  of  coal  feeding  device  invented  by  Mr.  W. 
R.  Dunn,  superintendent  of  the  Vulcanite  Portland  Cement  Co., 
and  designed  to  give  a  more  intimate  mixture  of  air  and  coal 
than  is  secured  by  ordinary  feeders.  It  will  be  noted  that 
the  coal  drops  through  a  number  of  openings  in  the  bottom  of 
the  conveyor  trough  while  air  is  sucked  in  above.  This  feeder 


202 


PORTLAND  CEMENT 


has  been  in  use  for  some  time  at  the  above  mentioned  plant, 
where  it  is  stated  its  introduction  saved  fuel. 

Mr.  Chas.  A.  Matcham,  then  Manager  of  the  Lehigh  Port- 


Fig.  56.— High  pressure  coal  burner. 

(C,  coal;  H.  P.  A.,  high  pressure  air; 

A.  A.,  atmospheric  air.) 


Fig.  57- 


land  Cement  Co.  in  1908  took  out  a  patent  on  a  method  for 
introducing  the  fuel  into  the  kiln  by  means  of  the  draft  of  the 
latter.  His  "natural  draft  system"  is  shown  in  Fig.  59  and  60. 
It  consists  in  dropping  the  coal  in  a  thin  sheet  across  a  slit 
in  the  end  of  the  kiln.  Air  sucked  in  by  the  draft  of  the  kiln 
through  this  slit  catches  up  the  coal  here  and  carries  it  into 
the  kiln.  No  fans  or  blowers  are  required  and  the  necessary 


BURNING 


203 


draft  is  secured  by  means  of  stacks  of  the  proper  height.  The 
coal  is  fed  out  of  a  bin  by  means  of  a  screw  conveyor  on  to 
an  inclined  plate,  £.  As  the  coal  slides  down  this,  it  spreads 


Fig.  58.— Dunn's  apparatus  for  mixing  fuel  and  air. 

out  in  a  thin  stream,  so  that  the  air  can  catch  it  readily.  The 
stream  of  coal  and  air  would  fall  to  the  bottom  of  the  kiln 
and  much  of  the  former  remain  unburned  if  air  only  entered  by 
the  slit,  therefore  it  is  necessary  to  admit  a  large  amount  of  air 
below  where  the  clinker  falls  from  the  kiln.  This  air  lifts  the 


Fig-  59-— Matcham's  natural  draft  coal  burner. 

flame  and  allows  the  coal  to  burn  before  falling  to  the  bottom 
of  the  kiln.  The  natural  draft  system  burns  a  good  hard  clinker 
but  one  somewhat  discolored  due  to  the  reducing  action  of  the 
coal  which  falls  down  in  it. 


204 


PORTLAND   CEMENT 


When  oil  is  employed  this  is  sprayed  into  the  kiln  by  means 
of  an  air  blast.  This  latter  is  usually  supplied  by  either  a  posi- 
tive pressure  blower  or  an  air  compressor.  For  oil  two  or  more 
burners  are  generally  necessary.  Fig.  61  shows  a  kiln  equipped 
with  oil  burning  appliances. 

Coal. 

The  coal  for  burning  is  usually  gas  slack  and  should  fill  the 
specifications  below : 

Per  cent. 

Volatile  and  combustible  matter    3°~45 

Fixed  Carbon 49-60 

Ash,  as  low  as  can  be  obtained  cheaply  and  not  over . . .  25 

In  the  Lehigh  district  good  gas  coal  can  be  obtained  with 
less  than  12  per  cent.  ash.  In  other  sections,  however,  poorer 
coal  has  to  be  bought.  The  ash,  when  under  the  limit  specified, 
of  course  merely  takes  away  from  the  full  value  of  the  coal. 
Above  this  limit  it  is  hard  to  burn  satisfactorily.  Sulphur 
has  no  effect  on  the  burning,  except  in  large  quantities.  Iron 
pyrites  are  hard,  and  consequently  may  not  pulverize.  When 
coal  containing  much  of  this  is  used  the  pyrites  may  remain  in 
coarse  crystals  after  grinding,  which  are  not  blown  in  the  kiln 
and  burned,  but  fall  from  the  nozzle  of  the  burner  among  the 
clinkers  and  remaining  unoxidized,  are  ground  with  the  clinker, 
causing  the  resulting  cement  to  develop  brown  stains.  Practi- 
cally none  of  the  sulphur  of  the  coal  enters  the  cement,  except 
as  above. 

TABLE  XVI.— ANALYSES  OF  COALS  USED  FOR  BURNING  CEMENT. 


From 

Moisture 

Volatile 
combustible 
matter 

Fixed  carbon 

Ash 

Wellston    Ohio   • 

2-94% 
1.38 
2.T5 
7-50 
0.82 
6.59 
2.10 
2.32 

4L96% 
35-04 
34.20 
30.70 
33-76 
34-97 
29.63 
27.08 

42.82^ 
56.03 

57-49 
53.8o 

61.57 
48.85 
51.28 
47.34 

12.27/0 

6.27 
6.16 
8.00 

3.85 
8.00 
16.99 
23.26 

Fairmont   ^^    Va  

Hocking  Valley 

Poor  quality  Penn'a... 
Poor  quality  Penn'a... 

The  coal  for  burning  is  usually  crushed  in  pot  crushers  or 


Fig.  60.— Matcham  natural  draft  system— Allentown  Portland  Cement  Co. 


Fig.  61.— System  for  burning  oil — Great  Western  Portland  Cement  Co..  Mildred,  Kans. 
(Kilns  and  blowers  driven  by  Wagner  Electric  Co.  motors). 


BURNING  2O5 

between  rolls,  dried  in  a  special  form  of  rotary  dryer  and  finely 
pulverized  in  tube  mills,  Fuller-Lehigh  Mills,  Raymond  Mills,  or 
Griffin  Mills.  In  some  plants  using  a  tube  mill,  this  is  preceded 
by  a  ball  mill  or  a  Williams  mill,  and  in  some,  the  coal  is  sent 
direct  from  the  pile  to  the  dryers  and  thence  through  the  rolls. 
The  Fuller-Lehigh  Mill  is  now  generally  considered  one  of  the 
most  efficient  mills  for  grinding  coal  as  among  other  things  it 
gives  greater  output  for  the  powrer  required  to  operate  it. 

Coal  Dryers. 

Three  or  four  forms  of  coal  dryers  are  in  use  for  drying 
coal  for  cement  burning.  A  common  form  consists  of  a  rotary 
cylinder  with  shelves,  and  in  general  similar  to  the  dryers  used 
for  rock;  except  that  it  is  encased  in  brick- work  and  that  the 
products  of  combustion  pass  around  it  and  then,  after  cooling 
somewhat,  back  through  it,  instead  of  directly  through  it  as 
with  the  rock  dryers. 

A  number  of  forms  of  special  patented  dryers  are  upon  the 
market  and  these  have  greater  efficiency  in  drying  coal  than  the 
one  just  mentioned.  The  dryers  of  this  type  used  chiefly  in 
the  cement  industry  are  the  Matcham  dryer,  the  Cummer  dryer, 
the  Ruggles-Coles  dryer,  the  Bartlett  and  Snow  dryer  and  the 
Meade  dryer. 

The  Meade  "Multi-tubular  Dryer"  is  shown  in  Fig.  62.  It' 
consists  of  an  outer  shell  and  a  series  of  four  drums  located 
within  this  shell.  The  outer  shell  is  made  in  two  sections : 
the  feed  end  section  and  the  discharge  end  section.  The  material 
to  be  dried  is  delivered  to  the  feed  end  section  through 
the  feed  hopptr  and  spout,  shown  at  the  stack  end  of 
the  dryer.  The  feed  end  shell  is  fitted  with  a  series  of 
channel  iron  shelves  which  are  fastened  to  the  inside  of  the 
shell.  The  office  of  these  channel  iron  shelves  is  to  lift  the 
material  up  after  it  is  discharged  by  the  feed  spout  and  grad- 
ually feed  the  material  forward  to  the  series  of  inner  drums.  The 
material  to  be  dried  passes  through  the  series  of  drums  which 
are  arranged  concentrically  around  the  longitudinal  axis  of  the 
dryer.  The  feed  end  of  these  drums  terminates  in  a  diaphragm, 


206 


PORTLAND    CEMENT 


at  the  end  of  the  feed  shell.  The  drums  are  supported  by 
means  of  suitable  fixed  joints  and  expansion  joints  to  the  shell 
at  the  discharge  end  of  the  dryer.  The  dryer  furnace  is 
placed  near  the  feed  end  of  the  dryer.  Only  the  drums  which 
receive  the  material  pass  through  the  furnace.  The  hot  gases 
circulate  around  the  dryer  drums  in  the  combustion  chamber  and 
then  pass  out  through  the  dryer  shell  at  the  discharge  end  of 


Fig.  62.— Meade's  multi-tubular  dryer. 

the  machine.  During  the  passage  of  these  hot  gases  through 
this  shell  complete  circulation  of  the  gases  around  the  outside 
of  the  drums  is  maintained.  The  lower  end  of  this  dryer  shell 
terminates  in  a  hood.  When  the  hot  gases  reach  this  point 
they  are  drawn  through  the  drums  in  which  the  material  is 
being  passed  by  means  of  the  induced  draft  of  the  stack,  and 
then  pass  out  through  the  shell  at  the  feed  end  of  the  dryer 
and  thence  through  the  stack. 

There  is  a  perfect  circulation  of  the  hot  gases  around  the 


BURNING 


207 


outside  and  through  the  interior  of  each  drum,  and  since  there 
are  four  of  these  drums  within  the  main  shell  of  the  dryer  the 
stream  of  material  passing  through  the  dryer  is  broken  up  into 
a  number  of  streams  every  one  of  which  is  subjected  to  all  the 
heat  passing  through  the  dryer.  As  the  material  passing  through 
the  dryer  is  divided  into  a  number  of  thin  streams  it 
is  evident  that  the  coal  will  not  only  be  thoroughly  dried 
but  on  account  of  the  material  in  the  dryer  drums  being 
exposed  to  the  action  of  the  heat  in  thin  layers  it  can  readily 
be  seen  that  the  capacity  of  the  dryer  will  be  large.  After  the 
material  has  traversed  the  entire  length  of  the  interior  dryer 


Fig.  63.— Matcham  coal  dryer. 

drums  it  is  discharged  through  the  hood  of  the  dryer  into  suit- 
able elevating  and  conveying  machinery. 

The  "Matcham  Coal  Dryer"  used  extensively  in  the  Lehigh 
cement  region  of  Pennsylvania  is  shown  in  Fig.  63.  This 
dryer  consists  of  an  inclined  cylinder  mounted  on  steel  tires 
which  run  on  rollers.  The  cylinder  is  revolved  by  means  of  a 
girth  gear  and  pinion  at  an  approximate  speed  of  3  to  4  turns 
a  minute.  The  cylinder  is  30  ft.  long  and  4^2  ft.  in  diameter. 
It  revolves  partly  in  a  brick  housing  which  contains  the  fur- 
naces. The  hot  gases  pass  up  around  the  cylinder,  and  'this 
serves  to  cool  them  off  to  a  temperature  sufficiently  low  to  admit 
of  their  being  led  back  through  the  cylinder  by  the  flue  with- 
out setting  fire  to  the  coal.  The  gases  pass  up  through  the 


208 


PORTLAND 


cylinder  to  the  stack.     The  coal  is  fed  in  at  the  upper  end  and 
falls  out  at  the  lower. 

Fig.  64  shows  the  C.  O.  Bartlett  &  Snow  dryer.  This  con- 
sists of  a  cylinder  divided  into  four  compartments  by  passages. 
The  whole  is  encased  in  brick-work  and  revolves  on  steel  tires 
located  at  the  ends  outside  the  brick-work,  as  do  the  other 
dryers.  A  furnace  is  placed  at  one  end  and  the  products  of 
combustion  pass  from  this  into  the  brick  casing  and  travel 
through  this,  circulating  in  doing  so  around  the  cylinder  and 
through  the  passages  separating  the  compartments.  The  gases 


fr  -j',.'*~ ••.•....•"•.•.-.•..; .4-1:*^ 


Fig.  64. — Bartlett  and  Snow  dryer. 

do  not  come  in  direct  contact   with  the  coal,   which  is   fed  in 
at  the  upper  end  and  falls  out  at  the  lower. 

The  "Ruggles-Coles  dryer"  is  shown  in  Fig.  65  and  consists 
of  two  concentric  cylinders,  which  are  fastened  together  and 
revolve  on  steel  tires,  supported  by  bearing  wheels.  The  cy- 
linders are  driven  by  gearing  as  shown.  The  inner  cylinder  ex- 
tends beyond  the  outer  one  at  the  head  end,  and  is  connected 
with  a  brick  furnace  by  a  flue  lined  with  fire  brick.  The  prod- 
ucts of  combustion  from  the  furnace  pass  down  the  central 
flue,  and  then  back  between  the  two  cylinders.  The  coal  is  fed 
into  the  head  end  of  the  dryer  between  the  two  shells,  and  is 
caught  up  by  flights  on  the  inside  of  the  outer  shell  and  dropped 
on  the  hot  inner  shell.  As  the  machine  revolves  the  coal  drops 


BURNING 


209 


from  the  inner  shell  to  the  bottom  of  the  outer  one,  is  carried 
up  by  the  flights  and  again  dropped  on  the  hot  inner  shell,  etc., 
until  dried.  The  hot  gases  of  combustion  passing  up  between 


Fig.  65. — Ruggles-Coles  dryer. 

the  two  shells  also  help  to  dry  the  material  which  is  discharged 
through  the  centre  of  the  rear  end.  The  fan  is  used  to  create 
a  draft  through  the  cylinders. 

The  "Cummer  dryer"  is  shown  in  Fig.  66.  It  consists  of  an  iron 
cylinder  entirely  surrounded  by  a  brick  chamber.     The  cylinder 


Fig.  66.— Cummer  dryer. 

is  set  at  an  incline  and  revolves  on  trunnioned  bearings.  It  is 
provided  with  a  great  many  hooded  openings,  J,  so  arranged  that 
the  heated  air  and  gases  of  combustion  are  drawn  into  the  cylin- 


2IO  PORTLAND 

der  by  means  of  the  fan,  G.  A  furnace  provided  with  a  mechan- 
ical stoker  produces  the  heat.  The  hot  gases  are  drawn  into  the 
brick-work  chamber,  where  they  are  mingled  with  air  drawn  in 
through  the  registers,  E  and  O,  located  at  intervals  in  the  brick- 
work side  of  the  chamber,  and  their  temperature  reduced  by  the 
dilution  to  a  point  making  it  safe  for  them  to  come  in  contact 
with  the  coal.  The  mingled  air  and  gases  of  combustion  are  then 
drawn  through  the  openings,  /.,  and  up  through  the  cylinder.  The 
material  is  fed  into  the  cylinder  through  the  hopper,  P,  and  parts 
with  its  moisture  as  it  works  its  way  down  through  the  cylinder 
to  the  discharge,  K. 

At  the  plant  of  the  International  Portland  Cement  Co.,  Hull, 
Canada,  the  coal  is  dried  by  drawing  air  over  the  red  hot  cement 
clinker,  and  then  through  an  ordinary  dryer  (such  as  is  used  for 
rock)  with  a  fan.  This  serves  to  both  cool  the  clinker  and  dry 
the  coal. 

Pulverizing  the  Coal. 

When  Fuller-Lehigh,  Raymond  or  Griffin  Mills  are  used  to  pul- 
verize the  coal  it  is  usual  to  reduce  the  latter  to  one-half  inch  size, 
though  these  mills  are  used  occasionally  on  gas  slack  taking  it  just 
as  it  comes  from  the  pile.  Tube  mills  require  the  coal  to  be  crush- 
ed by  rolls  or  a  crusher.  In  a  few  instances,  ball  mills  have  been 
installed  to  do  this  work,,  but  have  generally  proved  unsatisfac- 
tory from  the  frequency  with  which  the  outer  screens  clog.  Two 
excellent  mills  for  preparing  coal  for  the  tub*  mill  are  the  Wil- 
liams mill  and  the  Stedman  cage  disintegrator.  They  are  cheap- 
er and  more  satisfactory  than  ball  mills.  The  Williams  mill  is 
described  on  page  127.  The  Stedman  disintegrator  is  shown  in 
Fig.  67.  It  is  of  the  centrifugal  type  and  consists  of  two  or 
more  circular  rings  studded  with  beaters  to  form  a  cage.  This 
cage  revolves  within  and  in  the  opposite  direction  from  another 
cage.  The  cages  revolve  at  a  peripheral  speed  of  about  150  feet 
per  second  and  about  one-half  the  power  is  consumed  in  mov- 
ing the  air  within  the  casing  and  overcoming  the  friction  of  the 
machine.  The  cages  are  driven  by  means  of  two  shafts  with 
pulleys  one  of  which  latter  is  driven  by  a  half  turn  belt  so  that 


BURNING  211 

the  cages  revolve  in  opposite  directions.  The  coal  is  of  course 
ground  between  the  two  cages  being  thrown  from  one  to  the 
other. 

There  are  a  number  of  mills  on  the  market  which  are  adver- 
tised to  crush  and  pulverize  coal  without  drying.  One  of  the 
best  known  of  these  machines  is  the  Aero  Pulverizer.  This  is 
shown  in  Fig.  68.  It  consists  of  three  communicating  chambers, 
each  slightly  larger  in  diameter  than  the  preceding  one,  in  which 
revolve  paddles  on  arms,  whose  length  corresponds  with  the  in- 


Fig.  67. — Steadman  cage  disintegrator. 

creased  diameter  of  the  chambers.  A  fourth  chamber  contains 
a  fan  which  is  used  to  draw  the  more  finely  pulverized  material 
from  one  chamber  to  the  next,  and  finally  to  deliver  it  under  the 
impetus  of  a  forced  blast  to  the  burner.  The  air  required  for 
pulverizing  purposes  is  admitted  with  the  coal  through  inlets,  in 
the  feed  device.  The  additional  air  required  for  purposes  of 
combustion  is  admitted  between  the  third  work  chamber  and  the 
fan  chamber,  and  may  be  regulated  so  as  to  produce  either  an 
oxidizing,  a  neutral  or  a  reducing  flame. 

No  dryer  is   required,   and  the  pulverized   fuel  is  blown  di- 
rectly from  the  grinder  into  the  furnace  by  the  fans  of  the  ma- 


212  PORTLAND  CEMENT 

chine.  From  what  the  author  can  learn  of  these  machines  from 
men  who  have  used  them,  they  do  not  grind  very  fine  and  re- 
quire about  30-40  H.P  for  every  ton  of  coal  pulverized  per 
hour.  Unless  two  are  installed  for  each  kiln,  or  one  which  can 
be  readily  moved  into  position  is  provided,  repairs  to  the  machine 
necessitate  shutting  down  of  the  kiln. 

The  following  table  shows  the  relative  efficiency  of  various 
grinders  per  H.  P.  hour  upon  coal  grinding  to  a  fineness  of 
92  per  cent,  passing  the  No.  100  sieve. 

RELATIVE  EFFICIENCY  OF  VARIOUS  PULVERIZERS  PER  H.  P.  HOUR 

Pounds 

Fuller-Lehigh  Mill . . .  * 160  to  200 

Griffin  Mill 120  to  160 

Aero  Pulverizer 50  to     6o)4 

Tube  Mill,  including  rolls 44^  to  66^ 

Coal  for  burning  Portland  cement  should  be  so  finely  ground 
that  at  least  92  per  cent.,  and  better  95  per  cent,  of  it,  will  pass 
a  No.  100  sieve.  The  degree  of  fineness  to  which  the  coal  is 
ground  affects  the  amount  of  coal  used  directly,  the  finer  the 
coal  the  less  will  be  needed.  Spackman  stated  in  a  paper  read 
before  the  Association  of  Portland  Cement  Manufacturers  that 
a  fineness  increase  of  I  per  cent,  over  75  per  cent,  through  a 
2OO-mesh  sieve  would  effect  a  saving  of  2  per  cent,  in  fuel. 
This  has  been  the  experience,  I  believe,  in  other  lines  than  cement 
in  which  powdered  coal  has  been  tried.  The  fineness  is  tested  by 
sieving  as  directed  for  testing  the  fineness  of  cement,  using  shot 
to  rap  the  coal  through  the  sieve. 

A  42  in.  Fuller-Lehigh  mill  will  grind  coal  from  rolls  to  a 
fineness  of  92  per  cent,  through  a  loo-mesh  screen  at  the  rate 
of  about  4  to  5  tons  per  hour  and  at  an  expenditure  of  50  horse 
power.  A  5'  6"  X  20'  tube  mill!  will  grind  enough  coal  for  a 
1,200  barrel  plant,  or  about  2}^  tons  per  hour,  taking  coal  rang- 
ing from  one-half  inch  lumps  down,  and  using  80  horse  power 
in  doing  so. 

The  capacity  of  a  coal  grinding  plant  will  depend  entirely  on 
the  condition  in  which  the  coal  is  received  at  the  mill  and  the 
thoroughness  with  which  the  coal  is  prepared  for  the  tube  mill 


BURNING  213 

or  Griffin  mill.  The  tube  mill  is  not  well  adapted  to  crushing 
coarse  material  and  where  it  is  used  considerable  economy  will 
be  effected  by  reducing  the  coal  to  one-fourth  inch  or  finer  by 
means  of  some  form  of  disintegrator  such  as  Williams  or  Sted- 
man  mill.  When  run  of  mine  coal  is  received,  the  best  treat- 
ment would  be  a  set  of  toothed  rolls  before  the  dryer,  then  the 
dryer,  followed  by  a  disintegrator  and  a  tube  mill  or  by  a  Fuller- 
Lehigh  or  a  Griffin  mill  alone. 

Explosions,  Storage  of  Coal,  Etc. 

In  order  to  avoid  dangerous  explosions  in  coal  mills,  the  roof 
should  be  so  ventilated  that  there  can  be  no  accumulation  of  gases 
here.  The  precautions  about  lights,  fire,  smoking  by  the  opera- 
tors, etc.,  that  are  usually  taken  in  connection  with  inflammable 
materials  should  also  be  observed.  When  tube  mills  catch  on  fire 
inside,  the  fire  may  be  smothered  with  steam ;  or  a  2o-lb.  drum  of 
liquid  sulphur  dioxide  gas  may  be  kept  and  used  for  this  purpose. 
The  mill  must  be  well  cleared  of  this  gas,  however,  before  work- 
men are  allowed  to  enter  it  to  prevent  their  asphyxiation.  Water 
is  ineffective  and  should  not  be  used  as  it  merely  stirs  up  a  dust, 
and  mixtures  of  coal  dust  and  air  are  very  explosive. 

O.  A.  Done,  writing  in  Engineering  News,  gives  the  following 
hints  on  the  prevention  of  spontaneous  ignition  in  coal  piles.  The 
amount  of  moisture  in  a  bituminous  coal  is  a  measure  of  the  risk 
of  spontaneous  combustion  when  the  fuel  is  stored.  Bituminous 
coal  should  not  contain  more  than  4.75  per  cent,  water.  Coal 
bins  should  be  of  steel  or  iron  protected  by  concrete  and  should 
be  roofed  over.  Free  air  passages  should  be  provided  around 
the  walls  and  beneath  the  bins  to  keep  the  pile  cool,  and  the 
depth  of  the  coal  should  never  exceed  12  feet.  It  is  useless  to 
provide  air  passages  in  the  body  of  the  pile  as  these  only  tend 
to  promote  oxidation;  similarly  cracks,  etc.,  in  the  walls  of  the 
fuel  bin  increase  the  risk. 

Several  investigations  have  been  recently  undertaken  to  de- 
termine the  loss  in  fuel  value  and  also  in  weight  undergone  by 
coal  in  storage.  Nearly  all  of  these  investigations  have  been 
made  upon  coals  of  the  middle  west,  however,  and  no  data  is 
available  upon  West  Virginia  and  Western  Pennsylvania  coals 


214 


PORTLAND  CEMENT 


used  throughout  the  Lehigh  District.  In  a  paper  read  before  the 
American  Institute  of  Chemical  Engineers,  June  22-24,  1910, 
A.  Bement  gave  results  of  tests  made  on  Illinois  bituminous  coals 
to  determine  the  changes  in  heating  power  and  weight  due  to  ex- 
posure in  air  and  to  storage  under  water;  also  the  tendency  of 
coals  to  disintegrate  by  slacking.  The  average  proximate  com- 
position (moist)  of  the  seams  in  the  three  fields  tested  is  as 
follows : 


Coal  seam 

Springfield 

Central 

Southern 

12  66 

IA  18 

96e 

Ash  • 

TO  7C 

jO  OI 

•uo 

JO   QQ 

77  23. 

l6  23 

7  T     C£ 

-in  -if\ 

70    78 

J.7  8l 

oy-jv 

JO  QQO 

jo  77/1 

II  188 

The  following  tables  give  results  of  tests  showing  changes  of 
weight  and  heating  power,  and  disposition  due  to  slacking: 
CHANGE  DUE  TO  EXPOSURE  TO  AIR  FOR  ONE  YEAR 


Coal  seam 

Heating 
power 
Per  cent. 

Weight 
Per  cent. 

Total 
Per  cent. 

-  O  Q3 

..      J    J  C 

2  08 

—i  8s 

—  2  2Q 

-  -A.  I  A 

o  18 

u.  ^7 

CHANGE  DUE  TO  STORAGE  UNDER  WATER  FOR  ONE  YEAR 


Coal  seam 

Heating 
power 
Per  cent. 

Weight 
Per  cent. 

Total 
Per  cent. 

Central 

0.44 

UOO 
O  8l 

0.79 

u.  /y 

APPROXIMATE  PERCENTAGE  DISPOSITION  OF  LUMP  COAI,  AFTER 
EXPOSURE  TO  AIR  FOR  ONE  YEAR 


Sizes  over 
coal  seam 

Ivump 

Egg 

ij^  inch 

%  inch 

&inch 

0 

Springfield  

35 
18 

18 
16 

22 
T  r 

IO 

18 

8 

16 

88 

A0 

1  / 

9 

•5 

°-5 

BURNING 


215 


Burning  with  Natural  and  Producer  Gas. 

Natural  gas  has  been  successfully  used  for  the  heating1  of  the 
kiln,  both  in  the  Kansas  field  and  at  Wampum,  Pa.  At  the 
plant  of  the  lola  Portland  Cement  Co.,  lola,  Kan.,  the  gas  is 
also  used  to  generate  power  for  grinding,  etc.,  in  gas  engines 
Producer  gas  has  been  tried  but  the  writer  knows  of  but  one 
plant  where  it  was  used  for  any  great  length  of  time,  that 
was  at  a  small  plant  in  Canada.  In  conversation,  the  man- 
ager of  this  plant  informed  the  author  that  they  considered  it  as 
cheap  as  powdered  coal,  but  saw  no  particular  advantage  in  its 
use.  The  question  has  been  raised  at  numerous  times  as  to 
whether  sufficient  heat  could  be  developed  by  its  use  to  secure  the 
proper  temperature  in  the  kiln  for  burning,  and  numerous  cal- 


Fig.  69.— Swindell  gas  producer  and  rotary  kiln 

culations  have  been   given   to   prove   that   without   regeneration 
producer  gas  could  not  be  used   for  burning  Portland  cement. 


2l6  PORTLAND  CEMENT 

The  fact  that  it  has  been  used  at  several  plants  should  effectually 
set  at  rest  this  contention.  The  temperature  required  for  ce- 
ment burning  has  unquestionably  been  placed  too  high,  however, 
and  most  calculations  have  considered  the  gas  as  cold,  whereas 
it  is  usually  introduced  hot  from  the  producer  into  the  kiln. 

The  Diamond  Portland  Cement  Co.,  Middle  Branch,  O.,  at  one 
time  had  a  Swindell  gas  producer  in  operation  heating  one  of 
their  kilns,  but  have  now  discontinued  its  use.  Fig.  69  shows 
the  installation  of  the  producer  at  this  plant.  The  gas  producer 
was  built  15  feet  in  front  of  the  kiln,  which  was  6  feet  in 
diameter  and  60  feet  long.  The  coal,  which  was  of  inferior 
quality  and  cost  only  $1.50  per  ton  was  introduced  into  the 
producer  by  means  of  sliding  hoppers.  Steam  and  air  were 
introduced  under  and  through  the  inclined  grates  by  means  of 
blowers.  The  air  used  for  combustion  was  preheated  by  pass- 
ing up  through  iron  tubes  built  in  the  walls  of  the  producer. 
The  air  and  gas  were  led  to  the  kiln  by  separate  flues  as  shown 
in  the  plan.  The  labor  required  to  operate  the  producers  amounted 
to  about  $y2  cents  per  barrel  of  cement  including  the  wages  of 
the  burners,  the  coal  consumption  amounted  to  130  Ibs.  per 
barrel  and  the  output  to  240  barrels  per  day.  In  order 
to  properly  clinker  the  materials,  it  was  found  necessary  to 
add  soda  ash  to  the  mix  to  lower  the  clinkering  temperature 
to  a  point  which  the  producer  gas  could  reach.  This  installation 
of  producers  was  here  found  unsatisfactory  and  was  finally  re- 
placed by  coal  burning  and  pulverizing  apparatus. 

Mr.  H.  F.  Spackman,  in  a  paper  read  at  a  meeting  of  the 
Cement  Manufacturers'  Association,  stated  that  in  a  plant  de- 
signed by  his  company,  producers  were  tried  in  connection  with 
powdered  coal  on  two  rotary  kilns,  60  feet  long  by  5  feet  in 
diameter,  burning  slurry  containing  60  per  cent,  water.  Actual 
figures  in  this  plant  obtained  on  a  two  or  three  months'  run,  were 
125  barrels  of  cement  per  day,  with  a  coal  consumption  of  135 
Ibs.  of  coal  per  barrel,  while  the  kilns  working  on  powdered  coal 
required  on  an  average  for  a  seven  months'  run  138  Ibs.  of  coal 
per  barrel.  To  greatly  overbalance  this  3  Ibs.  saving  in  coal, 
however,  was  the  fact  that  six  men  each  shift  of  24  hours  were 


BURNING  217 

required  to  work  the  producers  and  that  as  gas  slack  could  not 
be  employed  a  coal  costing  50  cents  a  ton  more  had  to  be  sub- 
stituted. 

All  attempts  to  burn  cement  by  producer  gas  were  confined  to 
a  period  about  five  years  ago  and  the  writer  knows  of  no  plants 
which  are  at  the  present  time  employing  it.  Powdered  coal  has 
the  advantage  over  gas  firing  in  that  the  inherent  losses  of  the 
gas  producer  are  overcome.  These  losses  are  by  no  means  small. 
It  is  estimated  that  the  average  loss  of  heat  in  the  gasification 
of  fuel,  due  to  complete  combustion  to  carbon  dioxide,  heat  radia- 
tion, etc.,  is  seldom  less  than  20  per  cent.  If  to  this  is  added 
the  loss  due  to  the  carbon  which  the  ash  carries  away  with  it  and 
the  coal  consumed  in  the  boiler  for  the  production  of  the  steam 
required  for  the  gas  producer,  it  is  safe  to  say  that  the  loss  may 
generally  be  considered  as  30  per  cent,  of  the  thermal  value  of 
the  coal. 

Furthermore,  with  gas  firing  the  ashes  have  to  be  handled 
and  disposed  of  while  with  pulverized  coal  the  ash  is  blown 
away  or  enters  the  clinker.  No  advantage  can  be  claimed  for 
gas  firing  which  can  not  also  be  claimed  for  coal  except  the  doubt- 
ful one  of  the  contamination  of  the  cement  by  the  ash.  As  was 
shown  in  a  succeeding  section,  about  half  the  coal  ash  goes 
up  the  chimney  and  it  is  very  doubtful  if  what  falls  down  into 
the  mix  does  not  form  hydraulic  compounds  with  the  lime  of 
the  latter.  It  is  certain  that  it  does  combine  with  the  lime  as 
is  shown  by  the  fact  that  practically  all  cement  is  soluble  in  dilute 
acid,  while  coal  ash  is  insoluble.  If,  therefore,  the  ash  did  not 
combine,  a  residue  of  at  least  one-half  per  cent,  would  be  left 
when  cement  is  treated  with  dilute  acid. 

Another  advantage  claimed  for  producer  gas  is  the  ease  with 
which  the  flame  can  be  regulated.  Analyses  of  the  flue  gases 
of  the  kiln  show  combustion  to  be  complete  with  about  20  per 
cent,  excess  air  which  is  as  good  as  could  be  expected  with  pro- 
ducer gas.  Furthermore,  pulverized  coal  is  of  almost  constant 
composition  throughout  long  periods  while  the  composition  of  gas 
varies  with  the  operation  of  the  producers,  etc. 

Coal  can  be  pulverized  for  less  than  it  can  be  gasified,  the 


2l8 


PORTLAND  CEMENT 


labor  of  handling  the  producers  alone  amounting  to  more  than 
it  costs  to  pulverize  coal.  The  cost  of  pulverizing  coal  rarely 
amounts  to  more  than  1^2  cents  per  barrel  of  cement  burned 
and  often  falls  below  this. 

Natural  gas  is  used  for  burning  cement  at  several  plants  in 
Kansas.  Its  use  has  passed  beyond  the  experimental  stage  and 
where  it  is  obtainable  it  is  of  course  the  cheapest  form  of  fuel. 
Natural  gas  is,  however,  found  in  too  few  localities  to  make  it 
generally  applicable  to  cement  burning,  and,  even  when  found, 
the  supply  is  limited  and  may  give  out  after  a  few  years.  Below 
are  analyses  of  the  gas  at  Tola,  Kans.,  and  at  Independence, 
Kans.,  at  both  of  which  places  Portland  cement  mills  are  using 
natural  gas  not  only  for  heating  the  kilns  but  also  for  generating 
power. 

ANALYSIS  OF   NATURAL  GAS  USED  FOR    BURNING  PORTLAND  CEMENT 
IN  KANSAS   (BAILEY). 


lola 

Independence 

0.00 

0.45 

7.76 
1.23 

0.90 

0.00 

89.66 

o.oo 
trace 
3-28 

0.33 
0.44 
0.97 
95-28 

Chapter  IX. 

COOLING    AND    GRINDING    THE    CLINKER,   STORING    AND 
PACKING  THE  CEMENT,  ETC. 


Cooling  the  Clinker. 

The  clinker  leaves  the  kiln  at  a  temperature  of  about  2,100°  F. 
It  is,  of  course,  entirely  too  hot  to  grind  and  must  be  cooled.  It 
has  generally  been  found  preferable  to  do  this  mechanically  in- 
stead of  letting  the  clinker  lie  in  heaps  and  cool  of  itself.  In 
some  mills  this  has  been  done  in  pits,  in  others  in  rotary  coolers, 
but  many  of  the  older  mills  still  use  the  upright  cooler  shown  in 
Fig.  70.  This  consists  of  an  upright  steel  cylinder  about  8  feet  in 
diameter  and  35  feet  high  provided  as  shown  with  baffle  plates 
and  shelves.  As  the  clinker  falls  over  these  it  meets  a  current  of 
air  blown  in  through  a  perforated  pipe  running  up  through  the 
center  of  the  cylinder  and  is  thus  cooled.  There  is  usually  one 
cooler  to  each  pair  of  60  foot  kilns  or  to  one  8  by  125  foot  kiln. 
Larger  coolers  are  also  employed  for  the  big  kilns.  The  clinker 
is  led  from  the  kilns  by  chutes  to  a  bucket  elevator  which 
carries  it  to  the  top  of  the  cooler.  Usually  water  is  added  tc 
the  clinker  in  a  steady  stream  as  it  falls  into  the  elevator  pit. 
This  helps  to  cool  the  clinker,  makes  it  more  brittle  and  easier 
to  grind  in  the  ball  mill  and  saves  the  elevator  from  handling 
such  very  hot  material.  There  is  probably  nothing  in  the  curing 
of  the  cement  or  the  hydration  of  the  free  lime,  since  any  of  the 
former  present  is  usually  locked  up  in  the  interior  of  the  clinker. 
The  writer  has  frequently  cooled  clinker  suddenly  by  plunging  it, 
red  hot  from  the  mouth  of  the  kilns,  into  water.  The  only  percep- 
tible effect  is  to  bleach  the  color  from  dark  greenish  black  to  nearly 
white.  If  this  clinker  is  dried  and  ground,  it  will  be  found  to  have 
pretty  much  the  same  properties  as  clinker  caught  at  the  same 
time  and  allowed  to  cool  slowly  in  air.  The  writer  has  never 
observed  that  unsound  cement  could  be  made  sound  by  this 
process.  It  does  take  up  some  water  (probably  on  the  outside  of 


22O 


PORTLAND  CEMENT 


the  lumps  only,  however),  as  a  loss  on  ignition  test  will  show. 
Such  clinker  is  easily  ground  and  the  resulting  cement  trowels 
nicely. 
The  clinker  is  usually  drawn  from  the  bottom  of  the  cooler  on 


Fig.  70.— Upright  clinker  cooler  (Mosser  &  Son) 

to  belt  conveyors,  or  else  into  barrows  and  carried  to  an  elevator, 
which  carries  it  up  to  the  bins  above  the  ball  mills  or  rolls,  which 
ever  are  used  to  grind  the  clinker. 


COOLING  AND  GRINDING  THE  CLINKER,  ETC.  221 

The  more  modern  mills  employ  a  rotary  cooler  (see  Fig.  71) 
which  consists  of  a  steel  shell  similar  to  that  of  the  kiln  and 

% 

mounted  on  friction  rollers  just  as  the  kiln  is  carried.  Usually  this 
is  lined  with  cast  iron  plates  which  are  bolted  in,  so  that  they  can  be 
easily  removed.  Occasionally,  however,  the  coolers  are  lined 
with  fire  brick  or  vitrified  brick.  One  cooler  is  generally  em- 
ployed for  each  kiln,  the  cooler  being  located  below  the  kiln  to 
permit  of  the  discharge  of  the  hot  clinker  directly  from  the  kiln 
into  the  cooler  by  means  of  a  chute.  The  air  for  cooling  is 
drawn  in  by  the  draft  of  the  kiln,  and  as  the  air  passes  from  the 
cooler  to  the  kiln,  such  coolers  act  as  preheaters  for  the  air 
entering  the  kiln.  As  every  pound  of  clinker  carries  out  of  the 
kiln  between  450  and  700  B.  t.  u.,  it  will  be  seen  that  this  practice 
should  save  between  11  and  15  pounds  of  coal  per  barrel  of 
clinker.  The  cast  iron  lining  plates  are  often  made  T-shaped  so 
that  when  they  are  inverted  and  bolted  in  the  kiln  they  will  form 
'shelves  running  lengthwise  with  the  latter.  These  shelves  act 
as  carriers,  lifting  the  hot  clinker  and  dropping  it  through  the 
current  of  air.  Water  is  sometimes  fed  in  at  the  upper  end  of 
the  cooler  to  help  cool  the  clinker. 

At  the  discharge  end  of  some  of  these  coolers,  for  about  3 
feet,  the  shell  is  perforated  with  holes  from  1*4  to  2  inches  in 
diameter,  while  at  the  end  itself  is  a  large  angle  iron  with  the 
flange  turned  in  so  as  to  hold  inside  of  the  coolers  any  large 
lumps  of  clinker  which  do  not  pass  through  the  holes,  making  a 
rotary  screen  out  of  the  lower  end  of  the  cooler.  The  large 
lumps  may  be  broken  up  by  an  attendant  with  a  bar  or  hammer, 
or  else  several  large  balls  may  be  placed  in  the  cooler  and  allowed 
to  roll  around  in  the  latter,  thus  serving  to  break  up  the  large 
pieces  of  clinker.  This  form  of  screen  cooler,  we  believe,  was 
first  introduced  at  the  plant  of  the  Louisville  Portland  Cement 
Company,  Speeds,  Indiana,  but  it  has  since  been  adopted  at  a 
number  of  mills. 

Occasionally  rotary  coolers  are  mounted  separately  from  the 
kilns  so  that  the  air  from  the  former  does  not  pass  into  the  latter. 
This  is  usually  done  where  the  lay  of  the  land  will  not  allow 
excavating  for  the  coolers.  When  so  located  the  clinker  is 


222  PORTLAND  CEMENT 

carried  from  the  kilns  to  the  cooler  by  means  of  a  bucket 
elevator  and  the  air  uor  cooling  may  be  either  drawn  through 
the  coolers  by  means  of  a  stack  at  the  upper  end  or  else  blown  in 
by  a  fan.  A  5  by  50  foot  cooler  will  easily  cool  800  barrels  of 
clinker  when  air  is  drawn  through  the  latter  by  natural  draft. 
If  water  is  used,  the  capacity  can  no  doubt  be  increased. 

The  clinker  usually  drops  from  the  coolers  on  to  belt  or  pan 
conveyors,  which  carry  it  to  the  clinker  grinding  department  or 
else  into  storage. 

One  of  the  New  York  state  mills,  at  one  time,  used  a  cooler 
which  consisted  of  a  water- jacketed  revolving  cylinder,  the  water 
entering  and  leaving  the  jacket  through  pipes  leading  from  a 
specially  designed  feeder  placed  in  the  center  of  the  discharge 
end  of  the  cooler.  The  water  after  leaving  the  cooler  was  used 
in  the  boilers,  the  cooler  simply  acting  as  a  feed-water  heater. 
These  coolers  are  said  to  have  worked  well,  and  to  have  cooled 
the  clinker  perfectly. 

Cooling  clinker  in  pits  has  been  tried  at  a  number  of  places, 
but  does  not  seem  to  have  worked  very  well  anywhere.  Some 
few  mills  convey  their  clinker  red-hot  out  into  the  fields  and 
allow  it  to  cool  naturally.  The  great  difficulty  with  this  system 
of  storage  is  the  conveying  of  the  red-hot  clinkers  out  into  the 
fields.  Getting  them  back  to  the  mills  is,  of  course,  easy  as  any 
of  the  coal  handling  devices,  such  as  aerial  cables  and  orange 
peel  buckets,  will  do  this  satisfactorily,  or  tunnels  provided  with 
belt  conveyors  under  the  piles  may  be  used. 

It  was  found  that  such  clinker,  provided  it  was  dry,  ground 
much  more  easily  than  clinker  fresh  from  the  kilns,  the  slaking 
of  the  free  lime  no  doubt  serving  to  help  break  down  the 
structure  of  the  material.  In  order  to  take  advantage  of  this 
fact,  a  number  of  mills  which  cool  their  clinker  by  means  of  one 
of  the  mechanical  devices  described  above  have  installed  systems 
for  seasoning  their  clinker.  By  cooling  the  clinker  first  it  is 
much  easier  handled  as  belt  conveyors  can  be  used  to  replace  the 
more  troublesome  pan  and  apron  conveyors  necessary  for  the 
hot  material  and  also  if  rotary  coolers  are  used  the  heat  in  the 
clinker  may  be  utilized  to  heat  the  air  entering  the  kiln  whereby 


Fig.  71.— Rotary  cooler,  Great  Western  Portland  Cement  Co.,  Mildred,  Kans. 
(Driven  by  Wagner  Electric  Co.  motors). 


Fig.  72.— Clinker  storage— Dexter  Portland  Cement  Co.,  Nazareth,  Pa. 


COOLING  AND  GRINDING  THE  CUNKER,   ETC.  223 

fuel  will  be  saved.  One  of  the  best  of  these  arrangements  is  that  of 
the  Dexter  Portland  Cement  Company,  at  Nazareth,  Pa.  (Fig.  72). 
This  storage  consists  of  a  pan  conveyor  which  is  supported  on 
a  steel  trestle  and  protected  by  a  roof.  The  conveyor  may  be 
discharged  at  fixed  points.  The  clinker  is  carried  out  and  de- 
posited underneath  this  conveyor  in  a  long  pile.  It  is  allowed 
to  remain  here  for  two  or  three  weeks,  when  it  is  drawn  out  by 
means  of  spouts  on  to  belts  in  two  underground  tunnels,  which 
run  lengthwise  under  the  clinker  piles.  No  roof  is  placed  over 
the  clinker  and  consequently  any  rain  which  falls  upon  it  helps 
to  season  it.  Owing  to  the  fact  that  in  very  rainy  weather  this 
clinker  when  drawn  from  the  pile  is  wet,  it  was  deemed  advisa- 
ble to  install  a  dryer  just  before  the  grinding  mills,  but  this 
dryer  is  only  used  occasionally  when  the  clinker  is  very  wet.  The 
capacity  of  the  storage  is  about  72,000  barrels  of  clinker.  The 
clinker  is  drawn  out  of  one  end  of  the  pile  while  it  is  being 
dropped  into  the  other. 

When  a  dryer  is  not  provided  a  roof  should  be  placed  over  the 
pile,  or  fresh  clinker  only  may  be  ground  in  wet  weather,  allow- 
ing the  pile  to  dry  itself  by  the  absorption  of  the  water  by  the 
lime  of  the  clinker,  and  using  seasoned  clinker  when  the  weather 
is  dry. 

Clinker  which  has  been  seasoned  has  absorbed  more  or  less 
water  and  carbon  dioxide,  the  quantity  usually  amounting  to  from 
2  to  4  per  cent.,  depending  on  the  length  -of  time  of  exposure 
and  atmospheric  conditions  during  this  period.  The  effect  of 
this  seasoning  is  to  improve  the  soundness  and  trowelling  pro- 
perties of  the  cement.  Seasoning  always,  however,  lowers  the 
specific  gravity  and  often  the  one  and  seven  day  tests  of  the  ce- 
ment made  therefrom. 

Adding  the  Retarder. 

Before  being  ground,  it  is  usual  to  mix  with  the  clinker  the 
gypsum  necessary  to  retard  the  setting  time  of  the  cement  (see 
Chapter  XVI).  The  gypsum  is  usually  received  at  the  plant  in  the 
form  of  small  lumps,  crushed  to  pass  a  one  inch  ring  screen.  In 
most  plants  the  retarder  is  added  by  hand  although  at  a  few, 


224  PORTLAND   CEMENT 

automatic  scales  are  used.  The  latter  have  not  always  proved 
successful,  the  usual  trouble  being  the  small  amount  of  gypsum 
(2-3  per  cent.)  added  to  the  clinker  and  the  difficulty  of  getting 
automatic  scales  which  will  handle  a  few  pounds  of  such  lumpy 
material  simultaneously  with  several  hundred  pounds  of  clinker. 

At  the  older  plants  where  the  clinker  is  wheeled  from  the 
coolers  to  the  grinding  department  the  gypsum  is  usually  added 
to  the  barrow  and  the  amount  added  is  determined  by  volume 
and  not  by  weight.  A  shallow  box  holding  the  desired  amount 
of  gypsum  is  used  and  this  is  filled  with  gypsum  and  struck  off 
level  with  the  top.  This  answers  the  purpose  very  well  and 
serves  to  control  the  gypsum  in  the  cement  within  narrow  limits. 
When  belts  are  used  to  convey  the  clinker,  these  usually  dump 
into  a  hopper  scale.  This  latter  may  be  either  automatic  or 
hand  controlled.  An  attendant  adds  the  gypsum,  by  means  of  a 
box  which  holds  the  correct  weight  of  gypsum  for  one  dump 
of  the  scales.  The  scales  if  automatic  are  usually  provided  with 
counters  or  if  operated  by  hand  the  attendant  keeps  tally  on  a 
board  so  that  an  account  of  the  amount  of  clinker  ground  may 
be  kept. 

At  one  time  plaster  of  Paris  was  employed  to  slow  the  setting 
time  of  cement  but  since  the  writer  pointed  out  in  the  first  edi- 
tion of  this  work  that  gypsum  was  fully  as  efficient  a  retarder  as 
plaster  of  Paris  and  as  it  costs  much  less,  the  former  has  almost 
entirely  taken  the  place  of  the  latter.  At  one  time  also,  Nova 
Scotia  gypsum  was  almost  universally  used  as  it  contains  a 
higher  percentage  of  sulphuric  anhydride  than  the  native  gyp- 
sums. Now  the  cheaper  American  mineral  has  replaced"  the 
imported  one  to  a  great  extent.  In  purchasing  gypsum,  the 
manufacturer  purchases  sulphur  trioxide  (SO3)  and  the  con- 
sideration with  him  is  usually  how  much  of  this  he  will  get  for 
his  money. 

Grinding  the  Clinker. 
The  clinker  is  ground  by  any  one  of  the  following  systems : 

SYSTEMS    USED    FOR    GRINDING    THE    CLINKER. 

A.     Fuller-Lchigh  Mill  preceded  by    (a)    ball   mill   provided 


COOUNG  AND  GRINDING  THE)  CLINKER,  ETC.  225 

with  perforated  plates  and  without  screens   (b)  set  of  crushing 
rolls. 

B.  Tube  Mill  preceded  by   (a)    Ball  Mill  with  screens    (b) 
Kominuter  with  screens,     (c)   Single  roll  Griffin  mill  (d)  three 
roll  Griffin  mill  (e)  Kent  mill  (f)  Sturtevant  mill  (g)  Hunting- 
ton  Mill. 

C.  Griffin  Mill  preceded  by  (a)  ball  mill  provided  with  per- 
forated plates  and  without  screens  (b)  Set  of  crushing  rolls  (c) 
Pot  crusher.     (Sometimes  followed  by  tube  mill,  See  B.) 

D.  Kent  Mill  and    (a)    screen  separator    (b)    air  separator. 
(Sometimes  followed  by  tube  mill,  see  B.) 

E.  Sturtevant  Mill  and  Newaygo  separator.     (Sometimes  fol- 
lowed by  tube  mill,  see  B.) 

F.  Huntingdon  Mill  preceded  by  rolls.     (Now  generally  fol- 
lowed by  tube  mill.     See  B.) 

G.  Edison  rolls  and  air  separators. 

Of  these  systems  the  last  three  so  far  have  found  only  a  limited 
use.  The  Huntingdon  mill  both  alone  and  followed  by  the  tube 
mill  is  used  only  by  the  Atlas  Portland  Cement  Co.  The  Edison 
rolls  and  air  separator  are  employed  only  by  the  Edison  Port- 
land Cement  Co.,  Stewartsv'lle,  N.  J.  The  plant  of  the  Ogden 
Portland  Cement  Co.,  Baker's  Spun,  Utah  is  equipped  with 
Sturtevant  mills  and  Newaygo  screens. 

It  is  usual  for  the  clinker  to  be  ground  by  the  same  type  of 
machinery  as  is  used  to  grind  the  raw  material.  The  principal 
reason  for  this  is  that  only  one  set  of  repair  parts  have  to  be 
carried  in  stock.  A  number  of  mills,  however,  use  ball  and 
tube  mills  to  grind  the  raw  materials  and  Griffin  mills  to  grind 
the  clinker,  the  idea  of  these  manufacturers  being  that  the  former 
is  the  better  of  the  two  for  soft  materials,  and  the  latter  the 
more  suited  to  the  hard  clinker.  The  tube  mill  is  also  popular- 
ly supposed  to  be  a  better  mixer  than  other  mills  but  this  is  not 
borne  out  by  practice,  and  the  general  experience  has  been  that 
the  mill  which  will  grind  the  raw  materials  finest  will  in  all 
cases  give  the  best  cement.  No  mill  holds  enough  material  to 
obtain  a  uniform  mix  where  this  is  not  secured  before  the  materials 
15 


226  PORTLAND  CEMENT 

reach  the  mill.     The  tube  mill  is  better  suited  to  wet  grinding 
than  other  mills,  and  hence  to  marl  and  clay. 

All  of  the  above  mills  have  been  described  in  Chapter  VIII. 

Stock  Houses. 

From  the  grinding  mill  the  finished  cement  goes  to  the  stock 
house.  This  usually  consists  of  a  long  low  frame  building  divid- 
ed into  bins,  by  means  of  wooden  partitions,  so  that  each  day's 
grinding  may  be  kept  separate.  These  bins  usually  hold  from 
1000-5000  barrels  and  are  arranged  either  on  each  side  of  a  cen- 
tral aisle  or  else  with  an  aisle  on  each  side.  The  parts  of  the 
bins  facing  the  aisles  are  stopped  up  by  means  of  boards  which 
may  be  easily  removed,  and  below  the  floor  of  the  aisles,  run 
screw  conveyors  to  the  packing  room,  which  is  usually  one  end  or 
a  large  room  in  the  middle  of  the  stock  house.  The  screw  con- 
veyors are  covered  with  boards,  except  in  front  of  the  bins  where 
gratings  three  or  four  feet  in  length  are  placed.  The  cement  is 
usually  brought  in  from  the  grinding  mills  by  an  overhead  screw 
conveyor,  from  the  trough  of  which  spouts  run  to  the  middle 
of  the  bins.  The  openings  in  the  trough  leading  into  the  spouts 
are  closed  by  iron  slides  or  gates  so  that  the  cement  may  be  run 
into  any  bin  desired  at  any  time.  When  it  is  desired  to  open  a 
bin  the  bottom  plank  is  removed  from  the  front  of  the  bin  and 
the  cement  is  allowed  to  run  into  the  screw  conveyor,  through  the 
grating.  When  it  ceases  to  run  of  itself,  a  scraper,  which  con- 
sists of  a  flat  iron  plate  about  6  in.  X  18  in.  from  the  middle  of 
which  a  long  handle  projects,  is  introduced  and  all  of  the  cement 
which  can  be  pulled  through  the  opening  conveniently  is  drawn 
into  the  conveyor,  after  which  the  remainder  of  the  boards 
are  taken  down,  and  the  rest  of  the  cement  is  drawn  into  the 
conveyor,  either  with  the  scraper  or  wheeled  by  barrows  to  the 
grating. 

To  do  away  with  the  manual  labor  required  by  such  a  method 
of  opening  a  bin,  stock  houses  provided  with  tunnels  running  under 
the  bins  are  used.  The  conveyors  are  located  in  the  tunnel  and  the 
bins  are  fixed  with  sloping  floors  and  spouts,  which  deliver  into 
the  conveyor.  Fig.  73  shows  a  type  of  stock  house  which  is  being 


COOLING  AND  GRINDING  THE  CLINKER,  ETC. 


227 


installed  with  various  modifications  by  many  of ,  the  newer  mills. 
It  will  be  seen  that  the  conveyors  are  in  concrete  passage-ways 
and  that  most  of  the  contents  of  the  bin  can  be  run  out  by  gravity. 
A  method  which  is  adapted  to  the  improvement  of  old  stock 
houses  is  to  put  in  small  conveyors  running  across  the  bins  and 
emptying  into  the  main  conveyors.  The  stock-house  of  the 
Universal  Portland  Cement  Company's  Chicago  plant1  consists 
of  four  cylindrical  Monier  concrete-steel  bins  in  a  group.  The 


Fig-  73.— Recent  form  of  stock  house. 

bins  are  25  feet  in  diameter  and  53  feet  high  and  hold  about 
7,500  barrels  each.     The  cement  is  tapped  out  below. 

Figure  74  shows  a  stock  house  of  this  type,  which  is  that  of 
the  Dewey  Portland  Cement  Co.  Its  construction  is  evident  from 
the  illustration. 

Packing. 
Cement  is  packed  into  wooden  barrels  holding  380  Ibs.  or  into 

1  Cement,  III,  4,  286  ;  Cement  and  Engineering  News,  1903,  p.  55. 


228 


PORTLAND  CEMENT 


paper  or  cloth  bags  holding  95  Ibs.  by  means  of  packers,  such  as 
are  used  for  packing  flour.  The  cement  is  packed  as  shipped  and 
the  bags  or  barrels  are  trucked  directly  to  the  cars.  For  this 
reason  the  packing  room  should  be  so  arranged  that  the  cars  to 
be  loaded  can  be  brought  alongside  of  the  room  and  a  shed  roof 


Plan    B-B 
Fig.  74. — Stock  house  of  the  Dewey  Portland  Cement  Co. 


should  be  run  out  over  the  cars  so  the  loading  will  not  be  in- 
terrupted by  rainy  weather.  Since  some  seasons  of  the  year  are 
much  busier  than  others,  the  packing  house  should  be  able  to  load 
and  ship  at  least  twice  as  much  cement  as  the  mill  can  make  in  a 
day.  The  floor  of  the  packing  room  should  be  on  a  level  with 
the  floor  of  the  cars  to  be  loaded.  Cloth  bags  are  used  much 
more  for  packing  cement  than  anything  else.  In  the  case  of 
cloth  bags  the  consumer  is  charged  with  the  value  of  the  bag,  10 
cents,  and  credited  by  10  cents  when  the  bag  is  returned.  The 
bags  are  all  marked  with  the  label  of  the  brand  and  so  each 


COOUNG  AND  GRINDING  THS  CLINKER,  ETC.  22Q 

manufacturer  knows  his  own  bags.     Barrels  and  paper  bags  are 
sold  to  the  customer  and  are  not  returnable. 

Methods  employed  for  bagging  the  cement  have  always  been 
of  the  crudest  kind.  The  Bates  valve  bags  and  machine  for 
rilling  these  have  recently  been  given  a  trial  in  the  cement 
industry  and  the  system  has  proved  very  successful.  It  is  being 
installed  in  a  number  of  the  new  plants  and  many  of  the  older 
ones  also  have  adopted  it  after  thoroughly  trying  it  out.  The 


CZcsecZ 


Closed 


Fig-  75-— Bates  valve  bag. 


system  does  away  with  many  of  the  defects  of  the  old  methods 
of  packing,  including  short  and  over  weight,  bags  coming  untied 
in  transit,  slowness  of  packing,  need  for  skilled  labor,  etc. 

The  Bates  system  primarily  depends  upon  a  novel  bag,  of 
which  the  fundamental  feature  is  a  valve  in  one  corner.  This 
valve  projects  into  the  bag  as  is  shown  in  Fig.  75.  It  is  made  by 
ripping  and  tearing  down  a  corner  of  the  bag  and  sewing  up  on 
the  dotted  line  shown  in  the  figure.  When  pressure  is  applied 


230  PORTLAND  CEMENT 

to  the  valve,  as  when  the  cement  comes  against  it,  the  valve 
closes. 

With  this  bag,  the  operation  of  filling  which  ordinarily  con- 
sists of  putting  the  material'm  the  bag  and  then  tying  it,  is  re- 
versed and  instead,  the  bag  is  first  tied  and  then  filled,  the  filling 
being  done  through  the  valve  by  means  of  a  special  bagging 
machine  which  will  be  described  a  little  further  on.  When 
paper  sacks  are  used,  these  are  closed  at  both  ends  in  the  bag 
factory,  where  the  valve  is  also  placed  in  the  bag  by  folding  and 
pasting.  The  cloth  bags  are  tied  on  a  special  machine  which 
is  capable  of  handling  25  bags  at  once.  This  machine  is  shown 
in  Fig.  76.  With  this  appliance  a  boy  can  tie  between  four  and 
five  thousand  bags  in  a  day  of  ten  hours.  The  tying  is  done 
much  more  thoroughly  than  is  usually  the  case  by  hand.  A  large 
amount  of  string  is  also  saved.  A  wire  ring  which  is  twisted  on 
to  the  bag  by  a  machine  so  as  to  close  the  latter  has  recently 
been  brought  out  for  use  with  this  system. 

To  fill  the  bag  the  operator  has  only  to  slip  the  tube  of  the  bag- 
ging machine  through  the  self-closing  valve  of  the  finished  bag 
(Fig.  77).  This  he  can  do  with  a  quick  one-hand  motion.  A 
lever  is  then  opened  which  permits  the  material  to  flow  into,  the 
bag.  The  material  flows  into  the  bag  in  a  thin  stream  about 
one  inch  in  diameter,  and  consequently  there  is  no  danger  of 
tearing  or  ripping  the  bag.  When  the  exact  quantity  of  cement 
has  been  fed  into  the  sack,  the  weight  of  the  bag  and  con- 
tents off-sets  a  counterpoise  at  the  opposite  end  of  an  evenly 
balanced  beam.  The  bag,  of  course,  begins  to  fall  and  simul- 
taneously with  this,  the  flow  of  material  is  shut  off.  The  bag 
has  only  to  move  one-eighth  of  an  inch  for  this  to  take  place.  It 
is  consequently  possible  to  make  a  very  nice  adjustment  of  the 
weight  by  this  means. 

When  the  bag  has  been  filled,  it  is  left  hanging  suspended 
by  the  valve  spout  in  a  position  breast  high  to  a  man.  From  this 
point  it  is  easily  tilted  down  to  the  truck  without  the  weight  of 
the  bag  being  felt  unduly  on  the  muscles  of  the  men's  arms. 

A  four  tube  bagging  machine  will  pack  about   1000  to   1500 


Fig.  76.— Bates  valve  bag  system.    Tying  rack. 


77.— Bates  valve  bag  system.     Packing  machine. 


COOUNG  AND  GRINDING  THE  CLINKER,   ETC.  23! 

barrels  per  day  of  ten  hours.     Two  men  are  required  to  operate 
the  machine  and  place  the  bag  on  the  trucks. 

The  bagging  machine  may  also  be  obtained  mounted  on  wheels 
and  carrying  its  own  motor  so  that  it  can  be  employed  to  bag 
material  which  is  stocked  upon  the  floors  and  in  bins  not  pro- 
vided with  conveyors.  This  machine  is  provided  with  horizontal 
conveyors  which  work  against  the  base  of  the  pile  and  scrape  the 
material  to  an  elevator  which  carries  it  up  to  a  bin  above  the 
spouts.  When  it  is  desired  to  pack  from  a  pile  the  machine  has 
merely  to  be  pushed  with  its  conveyor  against  the  material  and 
the  motor  started.  The  automatic  conveyors  of  the  machine  then 
elevate  the  material  from  the  pile  to  the  bin  of  the  machine  and 


\ 


Fig.  78.— Sampling  tube  for  use  with  Bates  valve  bags. 


in  order  to  have   a   constant   supply   for  bagging   it   is   merely 
necessary  to  keep  the  machine  pushed  against  the  pile. 

One  of  the  greatest  advantages  of  the  valve  bag  is  the  ease 
with  which  samples  may  be  drawn  from  a  shipment  of  cement. 
For  this  purpose  a  small  brass  tube  (Fig.  78)  is  provided.  This 
is  simply  thrust  into  the  bag  through  the  valve  of  the  latter  and 
the  cement  which  it  retains  is  withdrawn  for  sampling.  The 
excellency  of  this  device  and  the  speed  with  which  the  sampling 
can  be  done,  makes  it  possible  to  sample  a  large  number  of  bags  in 
the  time  formerly  occupied  in  cutting  and  tying  one  or  two. 

Nearly  all  cement  mills  have  a  cooper  shop  connected  with  the 
mill.  Some  of  these  shops  are  equipped  with  barrel  making  ma- 
chinery, and  at  others  all  the  work  is  done  by  hand.  At  the 
present  time,  however,  barrels  are  but  seldom  used  except  for 


232  PORTLAND  CEMENT 

export  and  water  shipments.  Even  for  the  latter,  double  duck 
bags  are  replacing  barrels  and  most  of  the  cement  shipped  from 
this  country  for  the  Panama  canal  was  so  packed. 

Power  Plant. 

The  grinding  proposition  of  a  modern  cement  mill  is  one  of 
considerable  magnitude.  A  3,000  barrel  a  day  plant  must  grind 
about  i, 600  tons  of  material  to  an  almost  impalpable  powder  every 
twenty-four  hours.  Nine  hundred  tons  of  this  represents  the 
raw  material  which  must  be  reduced  from  pieces  of  stone  as 
large  as  a  man  can  handle  to  such  a  degree  of  fineness  that  from 
90  to  98  per  cent,  of  the  powder  will  pass  a  loo-mesh  test  sieve. 
Another  600  tons  represents  the  slag  like  clinker  which  must 
be  pulverized  so  fine  that  at  least  92  per  cent,  of  it  will  pass  this 
sieve.  The  power  required  to  run  the  amount  of  machinery  nec- 
essary to  grind  this  quantity  of  material  is  probably  greater  than 
that  which  would  be  utilized  in  the  manufacture  of  a  similar  value 
of  any  other  commodity. 

The  size  of  the  power  plant  which  will  be  required  in  manufac- 
turing 3,000  barrels  of  cement  per  day  will  depend  largely  upon 
thi  class  of  material  to  be  ground,  upon  the  type  of  machinery 
used  to  do  this,  the  thoroughness  with  which  it  is  done,  as  well 
as  the  proper  installation  of  the  plant  itself  and  the  means  of 
transmitting  the  power  to  the  machinery.  The  cheapness  with 
which  cement  can  be  manufactured  will  hinge  largely  on  these 
points  and  hence  the  power  plant  of  an  up-to-date  cement  mill 
must  be  "dead  right"  and  embody  the  most  economic  devices  for 
the  production  and  use  of  steam.  The  boilers  must  be  of  the  most 
improved  type  and  the  engines  of  the  most  modern  pattern.  The 
latter  must  be  heavily  made  and  able  to  stand  continuous,  heavy 
duty.  The  general  character  of  the  power  generators  themselves 
and  the  arrangement  of  the  engine  and  boiler  rooms  is  similar 
to  that  of  other  manufacturing  enterprises  where  much  slow  mov- 
ing heavy  machinery  is  operated.  Cross  compound  condensing 
engines  of  the  Corliss  type  are  generally  employed,  although  in 
electrically  driven  mills  the  steam  turbine  has  been  used  success- 
fully. Not  only  must  the  engines  and  boilers  be  of  the  proper 


COOLING  AND  GRINDING  THE  CUNKER,  ETC.  233 

type,  but  the  distribution  of  the  power  to  the  mills  must  be 
effected  with  the  least  possible  loss  due  to  friction.  When  the 
transmission  is  non-electrical  short  powerful  shafts  are  used 
which  are  driven  by  belting  or  rope  drives,  directly  from  the 
engines,  and  which  transmit  the  power  to  crushers,  and  grinding 
mills. 

In  designing  the  power  plant  of  a  shaft  driven  cement  mill, 
it  has  usually  been  found  best  to  run  the  mills  grinding  raw 
material  with  one  engine  and  those  grinding  clinker  by  another, 
rather  than  to  use  one  large  engine  for  both.  It  has  also  been 
found  best  to  run  the  kilns  by  a  separate  engine  so  that  shut- 
downs may  be  avoided. 

The  electrical  transmission  of  power  is  now  considered  best 
for  cement  mills  as  this  permits  of  a  better  arrangement  of  the 
buildings  both  as  regards  future  extensions  and  the  bringing  in 
of  supplies.  In  addition  to  this  as  each  machine  is  run  by  a 
separate  motor  the  plant  is  not  affected  by  the  shutting  down 
of  any  particular  machine  and  the  operation  is  more  continuous. 
In  this  system,  the  engines  are  connected  direct  or  by  belting  to 
powerful  alternating  current  electric  generators  and  the  current 
from  these  is  carried  about  the  mills  by  copper  cables  and  dis- 
tributed to  motors  which  are  directly  connected  by  gearing  or 
belting  to  the  mills.  Usually  two  or  three  engines  of  equal 
power  are  employed  rather  than  one  large  one,  on  account  of  shut- 
downs. Where  water-power  is  at  hand  the  generators  have 
been  connected  to  powerful  turbines  and  power  thus  very  cheaply 
obtained. 

One  of  the  defects  of  mills  actuated  by  horizontal  pulleys  such 
as  the  Fuller-Lehigh  Mill  and  the  Griffin  Mill,  has  consisted  in 
the  necessity  of  driving  them  with  a  quarter  twist  belt.  In  the 
new  mill  of  the  Allentown  Portland  Cement  Co.,  this  has  been 
done  away  with  by  the  use  of  vertical  motors  to  drive  the  Fuller 
Mills.  At  the  plants  of  the  Universal  Portland  Cement  Co.,  the 
Fuller  mills  in  the  coal  grinding  department  are  driven  by 
means  of  these  vertical  motors.  Practically  all  of  the  newer 
mills  have  adopted  the  plan  of  driving  their  kilns  and  machinery 
in  outlying  buildings  by  means  of  individual  motors,  even  where 


234  PORTLAND  CEMENT 

the  rest  of  the  plant  is  shaft  driven.  In  such  a  plant  about  25 
per  cent,  of  the  power  is  transmitted  electrically. 

In  the  new  plant  of  the  Tidewater  Portland  Cement  Co.,  Union 
Bridge,  Md.,  not  only  the  kilns,  crushers  and  grinding  machinery 
will  be  motor  driven  but  also  the  conveyors  will  be  so  operated. 
Each  conveyor  and  elevator  will  have  its  own  individual  motor, 
doing  away  with  practically  all  shafting  in  this  mill. 

A  few  of  the  western  plants  have  been  able  to  make  use  of 
cheap  hydro-electric  power  in  their  grinding.  In  practically  all 
cases,  the  power  has  been  purchased  from  some  large  outside 
corporation  developing  water  falls.  Among  the  mills  at  which 
this  has  been  done  may  be  mentioned  the  Santa  Cruz  Portland 
Cement  Co.  and  the  Cowell  Portland  Cement  Co.,  both  of 
California  and  the  Superior  Portland  Cement  Co.,  of  Baker, 
Washington.  At  some  of  the  Kansas  plants,  gas  engines  have 
been  installed  using  natural  gas  for  power.  These  mills  also  use 
natural  gas  for  burning. 

At  the  new  plants  of  the  Universal  Portland  Cement  Co.,  a 
subsidiary  concern  of  the  United  States  Steel  Corporation,  the 
waste  gases  from  the  blast-furnace  are  used  to  generate  the 
power  required  for  cement  manufacture.  The  gas  engines  are 
located  at  the  furnace  and  are  connected  to  generators.  The 
power  is  transmitted  some  distance  in  each  case  to  the  cement 
mill. 

The  actual  power  which  will  be  required  by  any  cement 
mill  as  we  have  said  before,  will  depend  entirely  upon  circum- 
stances. To  operate  a  mill  making  3,000  barrels  of  cement  from 
cement-rock  and  limestone,  engines  with  a  normal  rating  of  at 
least  3,000  horse  power  will  be  required.  A  mill  of  this  size, 
working  on  marl  and  clay,  will  require  a  little  less  while  one  on 
clay  and  limestone  will  require  a  little  more.  In  general,  it  may 
be  said  that  it  will  require  from  0.8  to  1.2  horse  power  for  each 
barrel  per  day  capacity  of  the  mill  to  operate  the  machinery. 
Faulty  installation  and  very  hard  raw  materials  may  easily  run 
this  figure  up  to  1.5  horse  power  per  barrel  of  cement  per  day 
capacity.  Roughly  speaking,  about  two-thirds  of  this  power 
will  be  required  to  run  the  grinding  mills ;  and  on  dry  materials 


COOLING  AND  GRINDING  THE  CLINKER,  ETC.  235 


Fig-  79.— Plan  and  section  of  the  Egyptian  Portland  Cement  Co.'s  works  at 
Fenion,  Mich.     (Engineering  Record.) 


236  PORTLAND 

of  average  hardness,  such  as  limestone  and  cement-rock,  this  will 
be  about  evenly  distributed  between  the  two  grinding  depart- 
ments. 

Complete  Equipment  of  Plants. 

Fig.  79  shows  the  arrangement  of  the  machinery  .and  the  dis- 
tribution of  power,  etc.,  in  a  modern  wet  process  plant;  while 
Fig.  80  shows  that  of  a  dry  process  mill.  In  the  latter  all  the 
machinery  is  driven  by  motors.  In  addition  to  the  plant  for 
manufacturing  ordinary  Portland  cement,  which  is  shown  in  the 
illustration,  this  company  will  also  have  a  plant  for  the  manu- 
facture of  white  Portland  cement. 

Table  XVII  which  follows  shows  the  mechanical  equipment  of 
eight  modern  Portland  cement  plants. 

TABLE  XVII.— SHOWING  THE  MECHANICAL  EQUIPMENT  OF  SOME 
MODERN  PORTLAND  CEMENT  PLANTS. 

Allentown    Portland    Cement    Co.1 

Materials — Cement-rock  xand    limestone.     Dry    (proqess.     Fuel — coal. 
Capacity — 2,400  barrels  daily.     Location — Evansville,  Pa. 
Quarry   Equipment. 

Deep  well  drilling  machine. 
End  dump  cars,  capacity  75  cu.  ft. 

Electric  hoists,  incline  and  automatic  car  dumping  arrangement. 
Stone  House. 

i  No.  10  McCully  crusher. 
3  No.  6l/2  Lehigh  crushers. 
I  Motor  250  H.  P.  used  to  drive  crushers. 

3  Waste  Heat  Dryers,  7'  X  50'. 

I  Motor  50  H.  P.  for  driving  all  above. 
Stone  Storage,   capacity  5,000  tons. 

1  Volume   mixing   apparatus. 
Raw  Mill. 

2  No.   8   Krupp   ball    mills,    without    screens,    each    driven    by    a    50 

H.    P.    motor. 

8  Fuller-Lehigh  mills,  42",  each  driven  by  a  75  H.  P.  vertical  motor. 
Kiln  Room. 

4  Rotary   kilns    (Wetherill)    8'    X    120'    each    driven    by   30    H.    P. 

variable   speed  motor. 
4  Rotary  coolers,  5'  X   5<>'  all  driven  from  a  line  shaft  by  one  50 

H.  P.  motor. 
Clinker   storage  consisting  of   steel  trestle  above  and  tunnel  below, 

with   belts   for   conveying. 

1  Chemical  Engineer,  g,  p.  127. 


COOLING  AND  GRINDING  THE  CUNKER,  ETC.  237 


Fig.  80.— Plan  of  the  Tidewater  Portland  Cement  Company's  Portland 
cement  plant,  at  Union  Bridge,  Md. 


238  PORTLAND  CEMENT 

TABLE  XVII.— (Continued.) 

Finishing  Mill. 

i   No.  8  Krupp  ball   mill,  without   screens,  driven  by  50  H.   P. 

motor. 

10  Fuller-Lehigh  mills,  42",  each  driven  by  a  75  H.  P.  vertical 

motor. 

Stock  house   with  a  capacity   of  80,000  barrels. 

4  Bates  automatic  valve  bag  packers. 

Fuel  Mill 

1  Set  rolls,  driven  by  40  H.   P.  motor. 

2  Matcham  coal  dryers,  driven  by  30  H.  P. 

2  Fuller-Lehigh  mills,  42",  75  H.  P.  motor  for  each. 

Coal  storage  and  mechanical  conveyor  for  handling  coal  as  unloaded. 

Power  Plant. 

3  Wetherill  cross-compound  condensing  engines,   direct-connected   to 
(Westinghouse)    a-c.  generators,  937  K.  V.  A.  each. 

i  Relay  unit. 

I  Motor  generator  set  for  exciting. 

I  Engine   driven    generator    for    exciting. 

5  Rust  vertical  tubular  boilers,  40  H.   P.   each. 

5  Sets  Lehigh  stokers. 

1  Traveling  crane,    10  tons. 

Mesta  barometric  condenser,   pumps,   etc. 

All   machinery   is   motor   driven,   and   most  of    it   by   individual  motors. 
Buildings  are  of  steel  and  plastered  expanded  metal. 

Clinchfield   Portland    Cement    Corporation.1 

Materials — limestone  and  shale.     Dry  process.     Fuel — coal. 
Capacity — 3,000  barrels   daily.     Location — Kingsport,   Tenn. 

Quarry  Equipment. 

3  No.  6  Gates  gyratory  crushers  driven  by  motors. 

2  Horizontal   high    speed   engines,    125    H.    P.   each    direct-connected 

to  two-phase,  22o-volt,  200  kw.  generators. 
I  Ingersoll-Rand    belt    driven    air    compressor. 
Rock  drills,  cars,  incline,   electric  hoist,   storage  bin,   etc. 
15  Steel    hopper    bottomed    railroad    cars    for    transporting   crushed 

stone  to   the   mill. 

I  Pair   Jeffrey    spiked    rolls    for    shale. 

Shale    storage   divided    into    three    bins.    Belt    conveyors    carry   the 
shale  to  the  mill. 

1  Manufacturers  Record,  59,  p.  49. 


COOLING  AND  GRINDING  THE  CLINKER,  ETC.  239 

TABLE  XVIL-  (Continued.} 
Stone  House. 

Richardson    automatic   scales    for  mixing. 

2  Pennsylvania  crushers,  (Hammer  Mills),  type  S-5,  each  driven 
by  its  own  75  H.  P.  motor. 

Raw  Mill. 

5  Pennsylvania    crushers,    type    S-6,    each    driven    by    a    100    H.    P. 

motor. 
9  Allis-Chalmers  tube  mills,  sl/2'  X  22'  each,  driven  by  a  90  H.  P. 

motor. 

Kiln  Room. 

5  Rotary  kilns,  8'  X   125',  operated  by  variable  speed  motors. 
Clinker  pits,  no  coolers,  clinker  storage  without  roof, 
i  Dryer   for   drying  clinker   in   wet   weather. 

Clinker  Mill. 

i  Set  corrugated  clinker  rolls. 

12  Griffin  mills,  40',  driven  each  by  a  75  H.  P.  motor. 
Reinforced  concrete  stock  house,  capacity  50,000  barrels. 
Bates  automatic  packing  machines. 

Fuel  Mill. 

1  Ruggles-Coles  dryer,  type  9  A,  30',  motor  driven. 
5  Raymond  pulverizers,  motor  driven. 

Power   Plant. 

Babcock   and  Wilcox  water  tube  boilers. 

2  Allis-Chalmers  steam  turbines,  direct  connected,  each  to  i.ooo  kw. 
generators. 

Pumps,   condensers,   etc. 

Crescent  Portland  Cement  Co.,  Mill  No.  2.1 

Materials — limestone   and   clay.     Dry  process.     Fuel — coal. 
Capacity — 3,000  barrels  daily.     Location — Wampum,   Pa. 

Quarry  Equipment. 

Air   drills. 

Buckets  of  i  ton  capacity  each,  hand  loaded,  placed  in  pairs  on 
flat  car  and  handled  by  locomotives  to  clay  storage  when  clay 
is  added,  and  the  buckets  are  conveyed  to  mill  by  aerial  tram- 
way. 

Dinkey  locomotives 

Marion   steam   shovel   for  clay. 

Fairbanks  scale  for  mixing. 

1  Engineering  Record,  6a,  p.  651. 


240  PORTLAND  CEMENT 

TABLE  XVII.— (  Continued. ) 
Stone  House. 

1  No.  8  McCully  crusher. 

2  No.  5  McCully  crushers. 
Stone  storage,  capacity  7,000  tons. 
2  Ruggles-Coles   rock   dryers. 

2  No.   3   Williams   hammer  mills. 

Raw  Mill. 

10  Raymond  impact  pulverizers. 

Kiln  Room. 

6  Rotary  kilns    (Vulcan),   8'   X    125',    equipped  with   high  pressure 
air  burners. 

3  Rotary  Ruggles-Coles  coolers. 

Finishing  Mill. 

2  Mosser  pot  crushers. 

4  Kent  mills  discharging  into. 

6  Prosser  (Krupp)   tube  mills,  6'  X  21'. 
Stock  house,  capacity  100,000  barrels. 
6  Howe  packers. 

3  Bates  automatic  valve  bag  packers. 

Fuel  Mill 

2  Ruggles-Coles   dryers. 

3  Raymond  bills. 

Coal  storage,  capacity  1,400  tons. 

Power  Plant. 

3  Ball  &  Wood  compound  condensing  engines,   direct   connected   to 

1,000  kw.,  a-c.  generators   (Western  Elec.  Co.). 
2  Ball  &  Wood  100  H.  P.  exciter  sets. 

2  Laidlow — Dunn — Gordon   compound  condensing  two   stage  air  com- 
pressor,   1,400   cu.    ft. 

8  McNaul  boilers,  300  H.   P.  each,  equipped  with  Roney  Stokers, 
i  Reinforced  concrete  stack  9'  X  180'. 
i  Centrifugal  pump,  capacity  3,000  gal.  per  min. 
Alberger  barometric  condenser,  boiler  pumps,  etc. 

Individual  motor  drives  with  6o-cycle,  3-phase,  44O-volt  induction 
motors,  are  used  throughout  the  plant.  Buildings  are  of  concrete  and 
steel. 

Dixie  Portland  Cement  Co.1 

Materials — limestone  and  shale.     Semi-wet  process.     Fuel — coal. 
Capacity — 5,000  barrels  daily.     Location — Copenhagen,  Tenn. 

1  Cement  and  Engineering  News,  20,  p.  230. 


COOUNG  AND  GRINDING  THE  CUNKER,  ETC.  24! 

TABLE  XVII.— (Continued.) 
Quarry  Equipment. 
Air  drills. 

2  Steam  shovels,  il/2  tons  each. 
Dump  cars. 

Electric  hoisting  engine. 
Belt  conveyor   (2,200')    from  shale  pit  to  mill. 

Stone  House. 

I  No.    18  McCully  crusher,   driven   by  its   own  electric  motor    (for 
limestone),    followed   by. 

1  Revolving  screen,   2"  openings,   followed  by. 

2  No.  6  McCully  crushers. 

6  Stone   storage   tanks,    capacity   300  tons   each. 
4  Hand-fired  rotary  dryers. 

4  Williams  hammer  mills   (for  shale). 

2  Shale  storage  tanks,  capacity  300  tons  each. 

Raw  Mill. 

22  Griffin  mills,  30'. 
2  Pug  mills. 

Kiln  Room. 

10  Rotary  kilns,  8'  X  125',  each  driven  by  a  30  H.  P.  motor. 
5  Revolving  coolers 

Finishing   Mill. 

26  Griffin  mills,  30'. 

Stock  house  with  a  capacity  of  300,000  barrels. 

7  Automatic   weighing  and   sacking   machines. 

Fuel  Mill. 

1  Coal   crusher. 

2  Rotary  coal  dryers. 

5  Fuller-Lehigh  mills,  42". 

Power  Plant. 

There  are  two  power  plants,   one  driving  the  raw  mill  and  one   for 
the  clinker  mill,   in   each  of  which  are 

2  Compound  condensing  engines,  1,000  H.  P.  Transmission  of  power 

to  lime  shafts  is  by  rope  drive    (American   system), 
i  Direct-current  generator,  400  kw. 
10  Heine  water  tube  boilers,  400  H.  P.  «ach. 
i  Reinforced   concrete  chimney,    150'  high. 

The   transmission   of   power   is   by  line  shafts.     Buildings   are   of   re- 
inforced   concrete    or    of    steel    and    plastered    expanded    metal.     Roofs 
are  of  corrugated  iron. 
16 


242  PORTLAND  CEMENT 

TABLE  XVII.— (Continued.} 
Egyptian  Portland  Cement  Co.1 

Materials — Marl   and   clay.     Wet  process.     Fuel — coal. 
Capacity — 1,400  barrels   daily.     Location — Fenton,   Mich. 

Excavating  Equipment. 

i  Marion  dipper  dredge. 

1  Machinery  boat  containing  stone  separator,  agitators  and  elevators. 

2  Scows,  capacity  50  cu.  yds.  each. 

1  Steam  tug. 

Raw  Mill 

2  Bonnot  slurry  pumps  for  unloading  scows. 

2  Marl  tanks. 

i  Dry  pan   for  clay. 

1  Pug  mill  for  mixing  marl  and  clay. 

3  Emery  mills,  42". 

2  Slurry    pits,    provided    with    agitators,    where    analyses    and    cor- 

rections are  made. 

2  Gates  tube  mills,  5'  X  22'. 

i    Slurry  storage  tank,  capacity  1,350  cu.  yds.,  provided  with  agita- 
tors. 

Kiln  Room. 

9  Rotary  kilns,  6'  X  60',  each  driven  by  its  own  engine, 
i  Pan  conveyor. 

1  Rotary   cooler    equipped    with   blower. 

Clinker  Mill. 

4  Gates  ball  mill,  No.  7. 

2  Gates  mills,  5'  X  22'. 

Concrete   storage  bins,  hand   packers. 

Fuel  Mill. 

i  Sturtevant    open    door   crusher, 
i  Bartlett  and  Snow  coal  dryer. 

1  No.   3  Williams   mill. 

2  Gates  tube  mills,  5'  X  22'. 
Power  Plant. 

2  Corliss  engines,  18"  X  36"  X  42". 

2  Water  tube  boilers,  500  H.  P.  each. 

2  Water  tube  boilers,  250  H.   P.  each. 

Pumps,  condensers,  feed-water  heaters,  etc. 

Transmission  of  power  is  by  line  shafts  and  rope  drives  (American 
system).  Buildings  have  steel  roof  trusses,  resting  on  concrete  pilasters 
with  brick  or  concrete  curtain  walls. 

1  Engineering  Record.  49,  p.  320. 


COOLING  AND  GRINDING  THE  CLINKER,  ETC.  243 

TABLE  XVII.— (Continued.) 
Union  Portland  Cement  Co.i 

Raw    materials — limestone    and    shale.     Dry    process.     Fuel — coal. 
Capacity — 2,500  barrels  daily.     Location — Devil's   Slide,  Utah. 
Quarry  Equipment. 

i  Bucyrus   steam   shovel,    70   ton. 
Cars   of   5   ton   capacity   each, 
i  Devenport  locomotive,  25  tons. 
Stone  House. 

1  No.  9  Gates  gyratory  crusher,  driven  by  an  85  H.  P.  motor. 

2  No.  6  Gates  gyratory  crushers,  driven  each  by  a  20  H.   P.  motor. 
2  Williams  hammer  mills,  driven  each  by  a  20  H.   P.  motor. 

4  Blending-bins,  capacity  1,000  tons  each. 
Mixing  scales. 

2  Allis-Chalmers  rotary  dryers,  6'  X  60',  equipped  with  Roney  stokers. 
Raw  Mill. 

4  Smidth  Kominuters,  No.  66,  driven  each  by  a  50  H.  P.  motor. 

5  Smidth  tube  mills,  5^'  X  22',  driven  each  by  a  120  H.  P.  motor. 
Kiln  Building. 

'  3  Rotary  kilns,  8'  X  150',  driven  each  by  a  50  H.  P.  motor,  high  pres- 
sure air  used  for  injecting  coal. 

3  Rotary  coolers,  6'   X   50'. 
Clinker   storage,   60'    X   80'. 

Clinker  Mill. 

4  Smidth  Kominuters,  No.  66,  driven  each  by  a  50  H.   P.  motor. 

6  Smidth  tube  mills,  5%'  X  22',  driven  each  by  a  120  H.  P.  motor. 
Fuel  Mill. 

I  Cummer  dryer. 

1  Smidth  Kominuter,  No.  66,  driven  by  a  50  H.  P.  motor. 

2  Smidth  tube  mills  Sl/2f  X  22',  driven  each  by  a  120  H.  P.  motor. 
2  Westinghouse   turbo-generator   sets,   each   1,500  kw.,   a-c.,   3-phase, 

3O-cycle. 

I  Synchronous   Fort  Wayne  motor-generator   set. 
i  Westinghouse  automatic  vertical  compound  engine,  direct-connected 

to  a  240  kw.,  25O-volt  d-c.  Fort  Wayne  generator, 
i  Cross    compound,    two    stage,    Laidlow-Dunn-Gordon    compressor, 

capacity   2,000   ctt.    ft.    per   min. 
i  Smaller  unit  'of  above  type  with  capacity  of  500  cu.   ft.  per  min. 

5  Heine   water  tube  boilers,   500  H.    P.,   each,   equipped   with   Roney 

stokers. 

Pumps,    Alberger    surface    condensers,    etc. 

All  drives  are  by  individual  induction  a-c.  motors,  except  kilns  which 
are  d-c.  motors. 

1  Engineering  Record,  57,  p.  125. 


244  PORTLAND 

TABLE  XVII.— (Continued. ) 
Universal  Portland  Cement  Co.,  Mill  No.  4.1 

Materials — blast-furnace  slag  and  limestone.  Dry  process.  Fuel — 
coal. 

Capacity — 5,000  barrels  daily.     Location — Buffington,   Ind. 
Both  raw  materials  are  delivered  to  the  mill  by  rail. 

Stone  House. 

3  No.  4  Gates  crushers. 

3  Rotary  dryers  for  limestone  5'  X  5o'. 

A  crusher  and  a  dryer  are  driven  by  a  20  H.  P.  motor. 

4  Rotary  dryers  for  slag  5'  X  50'. 

Dryers  are  driven  by  10  H.  P.  variable  speed  motors. 
Dryers  are  heated  by  pulverized  coal,  air  supplied  by  motor  driven 
blower. 

Raw  Mill. 

8  No.  8  Gates  ball  mills,  driven  each  by  a  40  H.  P.  motor. 

1  Set   electrically  operated  mixing   scales. 

12  Gates  tube  mills,  5'  X  22'  driven  each  by  a  100  H.  P.  motor. 

Kiln  Room. 

12  Rotary  kilns,  7^'  X   120',  driven  by  a  15  H.  P.  motor. 
Air  is  furnished  by  a  3  Buffalo  blowers,  driven  each  by  a  20  H.  P. 
motors. 

2  lo-ton   Alliance   electric  cranes   handle   the   clinker   with   three-ton 

grab  buckets.     Clinker  is  seasoned  in  piles. 

Finishing  Mill. 
12  Kent   mills. 
12  Newaygo  screens. 

A  mill  and  a  screen  are  driven  by  a  40  H.  P.  motor. 
15  Tube  mills,  5'  X  22',  driven  each  by  a  100  H.  P.  motor. 

Fuel  Mill. 

3  No.   I   Williams  coal  crusher. 
3  Dryers,  5^'  X  50'. 

A  crusher'  and  a  dryer  are  driven  by  a  motor. 

8  Fuller-Lehigh  mills,  33',  each  driven  by  a  40  H.  P.  vertical  motor. 

All  conveyors  and  elevators  throughout  the  plant  are  driven  by  in- 
dividual 5,  7^/2  and  10  H.  P.  motors.  Power  is  supplied  at  22,000  volts 
by  the  U.  S.  steel  corporation. 

1  Engineering  Record,  62,  p.  172. 


COOLING  AND  GRINDING  THE  CUNKER,  ETC.  245 

References  to  Descriptions  of  Plants. 

More  or  less  detailed  descriptions  of  the  following  plants  will 
be  found  in  the  books  and  journals  indicated.  The  plants  marked 
with  an  asterisk  (*)  are  wet  process  plants. 

Allentown  Portland  Cement  Co.,  Evansville,  Pa.,  Chemical  Engineer, 
Vol.  IX,  p.  127. 

Alma  Portland  Cement  Co.,  Wellston,  O.    The  Rotary  Kiln1,  p.  44. 

Alpha  Portland  Cement  Co.,  Alpha,  N.  J.  Engineering  News,  Vol. 
XLIV,  p.  313- 

Alsen's  American  Portland  Cement  Works,  West  Camp,  N.  Y.  The 
Rotary  Kiln,  p.  52;  Engineering  Record,  Vol.  XLVII,  p.  10. 

American  Cement  Co.,  Egypt,  Pa.    The  Rotary  Kiln,  p.  66. 

Atlantic  and  Gulf  Portland  Cement  Co.,  Ragland,  Ala.  Cement  and 
Engineeering  News,  Vol.  XXIII,  p.  117. 

Atlas  Portland  Cement  Co.  Proc.  Inst.  of  Civil  Eng.  (British),  Vol. 
CXLV,  p.  57. 

Bath  Portland  Cement  Co.,  Bath,  Pa.,  Engineering  Record,  Vol. 
UV,  p.  557- 

*Beaver  Portland  Cement  Co.,  Marlbank,  Canada.  The  Rotary  Kiln, 
p.  74 ;  Cement  and  Engineering  News,  VIII,  p.  72. 

*Bronson  Portland  Cement  Co.,  Bronson,  Mich.  The  Cement  In- 
dustry,2 p.  33.  Engineering  Record,  April  30,  1898. 

*Buckeye  Portland  Cement  Co.,  near  Bellefontaine,  O.  The  Cement 
Industry,  p.  52;  Engineering  Record,  October  15,  1898. 

Buckhorn  Portland  Cement  Co.,  Manheim,  W.  Va.  Engineering  News, 
Vol.  L.  p.  408. 

*Castalia  Portland  Cement  Co.,   Castalia,   O.    The  Rotary   Kiln. 

Canadian  Portland  Cement  Co.,  Port  Colborne,  Ont,  Cement  and 
Engineering  News,  Vol.  XXI,  p.  12. 

California  Portland  Cement  Co.,  Colton,  Cal.  Cement  and  Engineering 
News,  Vol.  XX,  p.  253;  Engineering  Record,  Vol.  LVII,  p.  269. 

Clinchfield  Portland  Cement  Co.,  Kingsport,  Tenn.  Manufacturers 
Record,  Vol.  LIX,  p.  49. 

3Clinton  Cement  Co.,  Pittsburg,  Pa.    The  Rotary  Kiln,  p.  82. 

Colorado  Portland  Cement  Co.,  Portland,  Colo.  Engineering  Record, 
Vol.  XLIX,  p.  223  and  242. 

Coplay  Cement  Co.,  Coplay,  Fa.  The  Cement  Industry,  p.  20  and  69. 
Engineering  Record,  December  18,  1897;  and  February  27,  1900. 

Cowell  Portland  Cement  Co.,  Cowell,  Cal.  Cement  and  Engineering 
News,  Vol.  XXI,  p.  104. 

1  The  Rotary  Kiln,  206  pages,  price  52.00.  I<athbury  &  Spackman,  Philadelphia,  1902. 
*  The  Cement  Industry,  225  pages,  price,  $3.00.  McGraw  Pub.  Co.,  New  York. 
3  Manufactures  Portland  Cement  from  slag  and  limestone. 


246  PORTLAND  CEMENT 

Crescent  Portland  Cement  Co.,  Wampum  Pa.  Engineering  Record, 
Vol.  LXII,  p.  651. 

*Detroit  Portland  Cement  Co.,  Fenton,  Mich.    The  Rotary  Kiln,  p.  86. 

Dexter  Portland  Cement  Co.,  Nazareth,  Pa.  Engineering  Record,  Vol. 
L.  160;  Engineering  and  Mining  Journal,  Vol.  LXXX,  p.  965. 

Dixie  Portland  Cement  Co.,  Copenhagen,  Tenn.  Cement  and  Engineer- 
ing News,  Vol.  XX,  p.  230. 

Edison  Portland  Cement  Co.,  near  Stewartsville,  N.  J.  Engineering 
Record,  Vol.  XLVIII  p.  796;  Engineering  News,  Vol.  L,  555;  Cement 
and  Engineering  News,  Vol.  XV,  p.  137. 

*Egyptian  Portland  Cement  Co.,  near  Fenton,  Mich.  Engineering 
Record,  Vol.  XLIX,  p.  320. 

*Empire  Portland  Cement  Co.,  Warners,  N.  Y.  Cement  Industry,  p. 
45.  Engineering  Record,  July  16,  1898. 

Hudson  Portland  Cement  Co.,  Hudson,  N.  Y.  Engineering  News,  Vol. 
L.  p.  70. 

*Hecla  Portland  Cement  Co.,  Bay  City,  Mich.  Engineering  News,  Vol. 
LI,  p.  243. 

*International  Portland  Cement  Co.,  Hull,  P.  O.,  Canada.  Engineer- 
ing Record,  Vol.  LI,  p.  106;  Cement  and  Engineering  News,  Vol.  XVII, 
p.  72. 

lola  Portland  Cement  Co.,  lola,  Kans.  Engineering  and  Mining  Jour- 
nal, February  16,  1901. 

Kansas  Portland  Cement  Co.,  Cement  City,  Mo.  Engineering  Record, 
Vol.  LH,  p.  170. 

Kosmos  Portland  Cement  Co.,  Kosmosdale,  Ky.  Cement  and  Engi- 
neering News,  Vol.  XVII,  p.  30;  Engineering  Record,  Vol.  LII,  p.  459; 
Cement  and  Engineering  News,  Vol.  XXI,  p.  258. 

Lawrence  Cement  Co.  of  Pennsylvania,  Siegfried,  Pa.  The  Rotary  Kiln, 
p.  96.  The  Cement  Industry,  p.  117.  Engineering  Record,  May  12,  1900. 

Los  Angeles  (Cal.)  Municipal  Cement  Plant,  Municipal  Engineering, 
Vol.  XXXVI,  p.  8.  Engineering  Record,  Vol.  LXII,  p.  330. 

Martin's  Creek  Portland  Cement  Co.,  Martin's  Creek,  Pa.  The  Ce- 
ment Industry,  p.  107.  Engineering  Record,  March  31,  1901. 

iMichigan  Alkali  Co.,  (now  Wyandotte  Portland  Cement  Co.)  Wyan- 
dotte,  Mich.  The  Rotary  Kiln,  p.  no;  Engineering  News,  June  7,  1900. 

^Michigan  Portland  Cement  Co.,  Coldwater,  Mich.  The  Cement  In- 
dustry, p.  78.  Engineering  Record,  February  25,  1899. 

National  Portland  Cement  Co.,  Martin's  Creek,  Pa.  Engineering  Rec- 
ord, Vol.  LI,  p.  288  and  316. 

Nazareth  Portland  Cement  Co.,  Nazareth,  Pa.  The  Cement  Industry, 
p.  85.  Engineering  Record,  December  16,  1899. 

Norfolk  Portland  Cement  Corporation,  Norfolk,  Va.  Cement  Age, 
Vol.  XII,  p.  91. 

1  Designed  to  use  alkali  waste  and  clay.    Now  uses  limestone  and  clay. 


COOLING  AND  GRINDING  THE  CLINKER,  ETC.  247 

Northampton  Portland  Cement  Co.,  Stockertown,  Pa.  Engineering 
Record,  Vol.  XLVIII,  p.  182. 

Ogden  Portland  Cement  Co.,  Baker's  Spur,  U.  Engineering  Record, 
Vol.  LXII,  p.  177. 

Oklahoma  Portland  Cement  Co.,  Ada,  Okla.  Cement  and  Engineering 
News,  Vol.  XXI,  p.  302. 

Pacific  Portland  Cement  Co.,  Mill  B,  Suisun,  Cal.  Cement  and  Engi- 
neering News,  Vol.  XXI,  p.  190;  Engineering  Record,  Vol.  LVII,  p.  662 

Pembina  Portland  Cement  Co.,  Milton,  N.  D.    The  Rotary  Kiln,  p.  124. 

Portland  Cement  Co.,  of  Utah,  Salt  Lake  City,  U.  The  Rotary  Kiln, 
p.  127.  Engineering  News,  Vol.  LXIV,  p.  243. 

St.  Louis  Portland  Cement  Co.,  Prospect  Hill,  Mo.  Engineering  Rec- 
ord, Vol.  XLVIII,  p.  36. 

Santa  Cruz  Portland  Cement  Co.,  Devenport,  Cal.  California  Journal 
of  Technology,  Vol.  X,  p.  28. 

Security  Cement  and  Lime  Co.,  Security,  Md.  Cement  and  Engineer- 
ing News,  Vol.  XX,  p.  230. 

Southern  States  Portland  Cement  Co.,  Rockmart,  Ga.  Cement  and  En- 
gineering News,  Vol.  XXI,  p.  265. 

Superior  Portland  Cement  Co.,  Superior,  O.  Cement  and  Engineer- 
ing News,  Vol.  XX,  p.  288. 

Superior  Portland  Cement  Co.,  Baker,  Wash.  Cement  and  Engineer- 
ing News,  Vol.  XX,  p.  325;  Engineering  Record,  Vol.  LVIII,  p.  205. 

Union  Portland  Cement  Co.,  Devil's  Slide,  U.  Engineering  Record, 
Vol.  LVII,  p.  125. 

Union  Sand  and  Materials  Co.,  Kansas  City,  Mo.  Cement  and  Engi- 
neering News,  Vol.  XXI,  p.  301. 

United  States  Government  Plant,  Roosevelt  Dam,  Ariz.  Municipal 
Engineering,  Vol.  XXXVI,  p.  71 ;  Cement  World,  Vol.  Ill,  p.  235. 

Universal  Portland  Cement  Co.,  Mill  No.  4,  Buffington,  Ind.  Engineer- 
ing Record,  Vol.  LXIII,  p.  172. 

Virginia  Portland  Cement  Co.,  Fordwick,  Va.  The  Cement  Industry, 
p.  132;  Engineering  Record,  July  28,  1900. 

Vulcanite  Portland  Cement  Co.,  near  Phillipsburg,  N.  J.  Cement  In- 
dustry, p.  96.  Engineering  Record,  May  6,  1899. 

*Wabash  Portland  Cement  Co.,  Stroh,  Ind.    The  Rotary  Kiln,  p.  128. 

*Western  Portland  Cement  Co.,  Yankton,  S.  D.  The  Cement  Industry, 
p.  60.  Engineering  Record,  November  19,  1898. 

Whitehall  Portland  Cement  Co.,  Cementon,  Pa.  The  Cement  Indus- 
try, p.  142.  Engineering  Record,  September  15,  1900.  Cement  and  En- 
gineering News,  Vol.  IX,  p.  23. 

Cost  of  Plant  and  Manufacture. 
A  great  many  itemized  statements,  showing  the  cost  of  erecting 


248  PORTLAND  CEMENT 

a  Portland  cement  plant  and  of  manufacturing  a  barrel  of  cement, 
have  been  published  in  the  last  few  years — no  two  of  them  agree- 
ing and  probably  none  of  them  coming  anywhere  near  the  truth. 
For  instance,  in  one  widely  quoted  estimate,  showing  the  average 
cost  of  making  a  barrel  of  Portland  cement  at  an  ideal  2,000  barrel 
plant  in  the  Lehigh  District,  the  estimator  has  assumed  that  5 
barrels  of  cement  can  be  made  from  one  ton  of  rock ;  whereas,  a 
tyro  chemist  knows  that  the  plant  is  doing  well  which  gets  3.3 
barrels  from  a  ton  of  raw  material.  Very  few  engineers  in  their 
estimates  of  the  cost  of  making  a  barrel  of  cement  have  included 
depreciation  of  buildings  and  the  actual  value  of  raw  material 
used.  This  latter  item  is  an  important  one,  in  spite  of  its  being 
overlooked.  For  example,  suppose  a  mill  using  marl  and  clay  has 
available  a  supply  of  marl  sufficient  for  the  manufacture  of  3,000,- 
ooo  barrels  of  cement,  and  cost  to  erect,  buy  the  land  and  put  in 
operation  $300,000.  Then  10  cents  at  least  should  be  added  to  the 
mill  cost  of  making  a  barrel  of  cement,  because  the  stockholders 
will  have  nothing  for  their  original  expenditure  (except  second- 
hand machinery)  when  they  will  have  made  their  3,000,000  bar- 
rels, and  hence  it  will  have  cost  them  10  cents  a  barrel  more  than 
the  actual  mill  expenditure  to  make  that  quantity  of  cement. 

Similarly,  much  has  been  written  as  to  the  cost  of  building  ce- 
ment plants  and  these  estimates  are  usually  very  much  like  those 
of  cost  and  leave  out  some  important  items.  For  instance,  in  one 
estimate  recently  published  in  a  bulletin  of  one  of  the  state  geolog- 
ical surveys,  the  machinery  is  probably  assumed  to  run  itself, 
since  no  figures  are  given  for  a  power  plant.  Even  experienced 
cement  engineers  often  come  very  wide  of  the  mark  in  their  esti- 
mates of  the  cost  of  erecting  plants,  and  it  is  no  uncommon  thing 
to  see  companies  run  through  a  liberal  estimate  of  cash  before 
their  plant  is  near  completion.  Often,  too,  plants  are  turned  over 
to  their  owners  by  the  engineers  erecting  them,  only  for  the  for- 
mer to  fird  $50,000  to  $100,000  must  be  spent,  in  order  to  make 
the  changes  necessary  for  a  successful,  economical  operation  of 
the  mill.  Plants  trying  new  machinery,  or  working  w^'th  new 
materials,  can  usually  count  on  doing  a  good  deal  of  altering  on 
starting  up;  and  plants  designed  and  built  by  engineers  in- 


COOUNG  AND  GRINDING  THE  CUNKER,  ETC.  249 

experienced  in  the  cement  industry  can  feel  reasonably  sure,  that 
the  practical  man  who  finally  comes  to  their  rescue  will  ask  for 
a  very  considerable  sum  of  money  to  put  them  on  an  economical 
working  basis. 

The  writer  does  not  believe  any  new  plants  will  be  built  having 
kilns  shorter  than  100  feet,  nor  does  he  believe  that  plants  small- 
er than  1,200  to  1, 600  barrels  capacity  can  be  made  to  operate 
economically  in  the  future.  In  general  it  may  be  said  that  a 
plant  with  a  capacity  of  1,200  barrels  daily  can  be  built  for 
$400,000  to  $500.000  and  one  of  2,500  barrels  daily  for  $700,000 
to  $850.000  depending  upon  the  type  of  machinery  and  buildings 
employed.  This  figure  does  not  include  the  cost  of  the  property, 
incorporation  charges,  etc.  These  estimates  are  of  course  very 
general.  They  imply  money  well  spent,  with  no  wasting,  and 
for  good  machinery. 

The  elements  entering  into  the  cost  of  manufacturing  a  barrel 
of  cement  are  as  follows : 

(1)  Labor. 

(2)  Supplies. 

(a)  Coal  for  burning. 

(b)  Coal  for  power. 

(c)  Gypsum. 

(d)  Limestone  or  clay. 

(e)  Repair  parts. 

(f)  Lubricants. 

(g)  Miscellaneous. 

(3)  Administrative. 

(a)  Mill  office. 

(b)  General  office. 

(c)  Laboratory. 

(4)  Fixed  charges. 

(a)  Interest  on  bonds,  if  any. 

(b)  Value  of  raw  materials  used, 
(•c)  Insurance  and  taxes. 

(d)  Depreciation  of  mill  buildings  and  machinery. 

The  cost  of  labor  varies  very  greatly  in  different  sections  of 
the  country.  The  cost  of  unskilled  labor  can  of  course  be  estimated 
fairly  well  by  any  one  familiar  with  the  local  conditions.  In  gen- 
eral it  may  be  said  that  a '1,200  to  1,600  barrel  mill  will  require 
one  unskilled  laborer  for  every  12  to  18  barrels  of  cement  pro- 


250  PORTLAND  CEMENT 

duced.  Of  the  skilled  laborers  there  will  be  needed  a  quarry 
foreman,  drillers,  millers,  burners,  engineers,  firemen,  packers, 
mill  foremen,  machinists  on  repair  work,  blacksmiths,  etc.  Of 
these  the  millers,  burners,  packers,  mill  foremen  and  some  of 
the  machinists  must  be  experienced  in  cement  mill  work,  and 
consequently  a  new  mill,  located  in  a  new  section  must  import 
these  men  from  one  of  the  old  established  centers  of  the  industry 
and  in  order  to  induce  these  men  to  leave  their  homes  must 
pay  them  much  higher  wages  than  the  older  mills  do.  In  the 
east  the  usual  charge  for  all  labor  (skilled  about  $2.5o~$3.oo. 
Unskilled,  $i.io-$i.5o)  is  between  12  and  20  cents  per  barrel. 

Of  the  supplies,  coal,  gypsum  and  limestone  (or  clay)  can  of 
course  be  calculated  fairly  closely.  Under  favorable  conditions, 
such  as  soft  raw  material  and  a  well  installed  power  generation 
and  transmission  system,  a  barrel  of  cement  can  be  made  with  55 
Ibs.  of  coal ;  and  even  hard  raw  materials  should  not  increase  this 
to  more  than  75  Ibs.  Poor  engines  and  boilers  and  faulty  power 
transmission,  however,  may  easily  raise  this  much  higher.  For 
the  amount  of  coal  used  to  burn  see  the  chapter  on  burning. 

Each  barrel  of  Portland  cement  has  added  to  it  from  8  to  12 
Ibs.  of  gypsum.  The  latter  is  the  limit  placed  by  the  standard 
specifications  and  the  former  is  the  usual  amount  used.  If  plas- 
ter of  Paris  is  used  in  place  of  gypsum  practically  the  same 
amount  is  required  and  its  cost  delivered  is  usually  about  twice  as 
great. 

The  cost  of  lubricants  varies  greatly,  but  under  good  manage- 
ment and  careful  attention  to  avoid  waste,  can  be  reduced  to  from 
0.7  to  i  cent  per  barrel. 

The  repair  parts  form  one  of  the  heaviest  of  the  supply  items 
of  a  cement  mill  and  depend  of  course  largely  on  the  type  of 
machinery  installed  to  the  grinding.  The  care  with  which  the 
machinery  is  used  also  has  a  large  influence  on  this  item.  Repair 
parts  may  cost  anywhere  from  6  to  10  cents  a  barrel,  even  with 
good  management. 

The  miscellaneous  supplies  usually  foot  up  to  about  i  to  2  cents 
a  barrel — dynamite  forming  one  of  the  heaviest  items  of  this. 
Theoretically,  the  container  in  which  cement  is  shipped  is  sup- 


COOUNG  AND  GRINDING  THE  CUNKER,   ETC.  25! 

posed  to  pay  for  itself  and  is  not  included  in  the  cost  of  mill  sup- 
plies. The  labor  of  packing  has  been  included  under  labor. 

The  administration  expenses  vary  greatly  with  the  size  of  the 
mill,  and  the  calibre  of  the  men  employed.  With  a  small  mill  em- 
ploying a  first-class  manager  and  chemist  and  good  assistants, 
this  may  figure  as  high  as  6  cents  a  barrel,  while  a  large  mill  may 
reduce  this  easily  to  2  or  3  cents  a  barrel. 

Of  the  fixed  charges,  taxes  and  insurance  usually  amount  to  I 
to  2  cents  a  barrel.  The  depreciation  of  mill  buildings  and  ma- 
chinery are  usually  figured  at  10  per  cent,  of  their  cost  erected, 
and  the  interest  on  bonds,  etc.,  can  of  course  be  calculated  with 
certainty.  To  calculate  the  value  of  the  raw  materials  used,  it  is 
necessary  to  know  the  amount  of  these  available,  when  the  cal- 
culation becomes  merely  one  for  arithmetic. 

The  cost  of  manufacturing  Portland  cement  may  therefore  be 
said  to  depend  on  (i)  the  location  of  the  mill  and  the  ease  with 
which  it  can  obtain  its  supplies,  (2)  the  cost  of  labor,  (3)  the 
efficiency  of  the  machinery  installed,  (4)  the  extent,  suitability 
and  softness  of  the  raw  materials,  and  (5)  the  management  and 
running  of  the  mill,  and  the  purchasing  of  its  supplies. 


ANALYTICAL  METHODS. 


Chapter    X. 


THE  ANALYSIS  OF  CEMENT. 


Preparation  of  the  Sample.1 

The  sample  is  usually  received  at  the  chemical  laboratory  in  a 
paper  or  cloth  bag  or  in  a  tin  box  or  can.  Here  the  sample  is 
well  mixed  by  passing  several  times  through  a  coarse  sieve,  and 
by  rolling  back  and  forth  on  a  sheet  of  paper,  or  better  still,  one 
of  oil  cloth.  When  thoroughly  well  mixed  it  is  spread  out  in 
a  thin  layer  on  the  paper,  or  oil  cloth,  and  divided  into  20  to 
30  little  squares  with  the  point  of  a  spatula  or  trowel.  A  small 
quantity  (about  I  or  2  grams)  of  cement  is  now  taken  from  each 
one  of  these  squares  with  the  trowel  or  spatula  point  and  these 
small  samples  are  mixed  and  5  to  10  grams  of  the  mixture  pre- 
pared as  described  in  the  next  paragraph  for  the  chemical  anal- 
ysis. The  main  portion  of  the  cement  is  then  replaced  in  the 
bag  or  bucket  and  used  for  the  physical  tests. 

In  order  that  the  solvents  used  to  decompose  the  cement  for 
analysis  may  do  their  work,  the  portion  weighed  out  must  con- 
tain no  coarse  pieces  of  clinker.  To  guard  against  this,  pass  the 
smaller  sample  through  a  No.  loo-mesh  test  sieve,  grinding  any 
residue  caught  upon  the  sieve  in  an  agate  mortar  until  it,  too, 
passes.  From  the  size  and  shape  of  the  ordinary  agate  mortar 
and  pestle  the  operation  of  grinding  is  very  fatiguing.  It  may  be 
much  facilitated,  however,  by  cutting  a  hole,  of  such  size  and 
shape  as  to  hold  the  mortar  firmly,  in  the  middle  of  a  block  of 
hard  wood,  a  foot  or  so  square.  The  pestle  is  then  fixed  in  a 
piece  of  round  brass  tubing  of  sufficient  bore,  or  else  in  a  round 
hard  wood  handle.  Several  mechanical  grinders  are  on  the  mar- 
ket, descriptions  of  which  may  be  found  in  the  trade  catalogues 
of  most  of  the  prominent  dealers  in  chemical  apparatus. 

1  See  also  Chapter  XIII  on  "  The  inspection  of  cement." 


THE    ANALYSIS    OF    CEMENT  253 

After  being  ground  the  sample  for  chemical  analysis  should  be 
placed  in  a  small  (one  or  two  ounce)  wide  mouth  bottle  and  tight- 
ly corked.  If  for  immediate  use  a  sample  or  coin  envelope  may 
be  substituted  for  the  bottle.  The  bottles  are  cheap  enough,  how- 
ever, and,  as  cement  rapidly  absorbs  water  and  carbon  dioxide 
from  the  air,  it  is  a  good  rule  to  use  them  altogether. 

DETERMINATION  OF  SILICA,  FERRIC  OXIDE  AND  ALUMINA, 
LIME  AND  MAGNESIA. 


Method  Proposed  by  the  Committee  on  Uniformity  in  the  Analy- 
sis of  Materials  of  the  Portland  Cement  Industry  of  the  New 
York  Section  of  the  Society  of  Chemical  Industry.1 


Solution. 

One-half  gram  of  the  finely  powdered  substance  is  to  be 
weighed  out  and,  if  a  limestone  or  unburned  mixture,  strongly 
ignited  in  a  covered  platinum  crucible  over  a  strong  blast  for  15 
minutes,  or  longer  if  the  blast  is  not  powerful  enough  to  effect 
complete  conversion  to  a  cement  in  this  time.  It  is  then  trans- 
ferred to  an  evaporating  dish,  preferably  of  platinum  for  the  sake 
of  celerity  in  evaporation,  moistened  with  enough  water  to  pre- 
vent lumping,  and  5  to  10  cc.  of  strong  HC1  added  and  digested 
with  the  aid  of  gentle  heat  and  agitation  until  solution  is  com- 
plete. Solution  may  be  aided  by  light  pressure  with  the  flattened 
end  of  a  glass  rod.2  The  solution  is  then  evaporated  to  dryness, 
as  far  as  this  may  be  possible  on  the  bath. 

Silica. 

The  residue  without  further  heating  is  treated  at  first  with  5 
to  10  cc.  of  strong  HC1  which  is  then  diluted  to  half  strength  or 
less,  or  upon  the  residue  may  be  poured  at  once  a  larger  volume 
of  acid  of  half  strength.  The  dish  is  then  covered  and  digestion 

1  This  committee  consisted  of  Messrs.  Clifford  Richardson,  Spencer  B.  Newberry  and 
H.  A.  Schaffer.    Their  various  reports  were  published  in  Journalof  the  Society  of  Chemical 
Industry,  XXI,  12,  830  and  1216  ;  Journal  American  Chemical  Society ;  XXV,  1180  and  XXVI, 
995;  and  Cement  and  Engineering  News,  XVI,  37. 

2  If  anything  remains  undecomposed  it  should  be  separated,   fused  with  a    little 
NaoCOg  dissolved  and  added  to  the  original  solution.    Of  course,  a  small  amount  of 
separated  non-gelatinous  silica  is  not  to  be  mistaken  for  undecomposed  matter. 


254  PORTLAND  CEMENT 

allowed  to  go  on  for  10  minutes  on  the  bath,  after  which  the  solu- 
tion is  filtered  and  the  separated  silica  washed  thoroughly  with 
water.  The  filtrate  is  again  evaporated  to  dryness,  the  residue 
without  further  heating,  taken  up  with  acid  and  water  and  the 
small  amount  of  silica  it  contains  separated  on  another  filter- 
paper.  The  papers  containing  the  residue  are  transferred  wet  to 
a  weighed  platinum  crucible,  dried,  ignited,  first  over  a  Bunsen 
burner  until  the  carbon  of  the  filter  is  completely  consumed,  and 
finally  over  the  blast  for  15  minutes  and  checked  by  a  further 
blasting  for  10  minutes  or  to  constant  weight.  The  silica,  if  great 
accuracy  is  desired,  is  treated  in  the  crucible  with  about  10  cc. 
of  HF1  and  four  drops  of  H2SO4  and  evaporated  over  a  low 
flame  to  complete  dryness.  The  small  residue  is  finally  blasted, 
for  a  minute  or  two,  cooled  and  weighed.  The  difference  be- 
tween this  weight  and  the  weight  previously  obtained  gives  the 
amount  of  silica.1 

Iron  Oxide  and  Alumina. 

The  filtrate,  about  250  cc.,  from  the  second  evaporation  for 
SiO2,  is  made  alkaline  with  NH4OH  after  adding  HC1,  if  need 
be,  to  insure  a  total  of  10  to  15  cc.  strong  acid,  and  boiled  to  ex- 
pel excess  of  NH3,  or  until  there  is  but  a  faint  odor  of  it,  and  the 
precipitated  iron  and  aluminum  hydrates,  after  settling,  are 
washed  once  by  decantation  and  slightly  on  the  filter.  Setting 
aside  the  filtrate,  the  precipitate  is  dissolved  in  hot  dilute  HC1, 
the  solution  passing  into  the  beaker  in  which  the  precipitation 
was  made.  The  aluminum  and  iron  are  then  reprecipitated  by 
NH4OPI,  boiled  and  the  second  precipitate  collected  and  washed 
on  the  same  filter  used  in  the  first  instance.  The  filter-paper, 
with  the  precipitate,  is  then  placed  in  a  weighed  platinum  cruci- 
ble, the  paper  burned  off  and  the  precipitate  ignited  and  finally 
blasted  5  minutes,  with  care  to  prevent  reduction,  cooled  and 
weighed  as  A12CX  +  Fe,O3.2 

1  For  ordinary  control  work  in  the  plant  laboratory  this  correction  may,  perhaps,  be 
neglected  ;  the  double  evaporation  never. 

2  This  precipitate  contains  TiO2,  P2O5.  Mn3O4. 


THE    ANALYSIS    OF    CEMENT  255 

Lime. 

To  the  combined  filtrate  from  the  A12O3  -f-  Fe2O3  precipitate  a 
few  drops  of  NH4OH  are  added,  and  the  solution  brought  to 
boiling.  To  the  boiling  solution  20  cc.  of  a  saturated  solution  of 
ammonium  oxalate  are  added,  and  the  boiling  continued  until  the 
precipitated  CaC2O4  assumes  a  well-defined  granular  form.  It 
is  then  allowed  to  stand  for  20  minutes,  or  until  the  precipitate 
has  settled,  and  then  filtered  and  washed.  The  precipitate  and 
filter  are  placed  wet  in  a  platinum  crucible,  and  the  paper  burned 
off  over  a  small  flame  of  a  Bunsen  burner.  It  is  then  ignited,  re- 
dissolved  in  HC1,  and  the  solution  made  up  to  100  cc.  with  water. 
Ammonia  is  added  in  slight  excess,  and  the  liquid  is  boiled.  If 
a  small  amount  of  A12O3  separates  this  is  filtered  out,  weighed, 
and  the  amount  added  to  that  found  in  the  first  determination, 
when  greater  accuracy  is  desired.  The  lime  is  then  reprecipitated 
by  ammonium  oxalate,  allowed  to  stand  until  settled,  filtered, 
and  washed,1  weighed  as  oxide  by  ignition  and  blasting  in  a  cov- 
ered crucible  to  constant  weight,  or  determined  with  dilute  stand- 
ard permanganate.2 

Magnesia. 

The  combined  filtrates  from  the  calcium  precipitates  are  acid- 
ified with  HC1  and  concentrated  on  the  steam-bath  to  about  150 
cc.,  10  cc.  of  saturated  solution  of  Na(NH4)HPO4  are  added, 
and  the  solution  boiled  for  several  minutes.  It  is  then  removed 
from  the  flame  and  cooled  by  placing  the  beaker  in  ice-water. 
After  cooling,  XH4OH  is  added  drop  by  drop  with  constant  stir- 
ring until  the  crystalline  ammonium-magnesium  ortho-phosphate 
begins  to  form,  and  then  in  moderate  excess,  the  stirring  being 
continued  for  several  minutes.  It  is  then  set  aside  for  several 
hours  in  a  cool  atmosphere  and  filtered.  The  precipitate  is  re- 
dissolved  in  hot  dilute  HC1,  the  solution  made  up  to  about  100 
cc.,  i  cc.  of  a  saturated  solution  of  Na(NH4)HPO4  added,  and 
ammonia  drop  by  drop,  with  constant  stirring  until  the  precipitate 
is  again  formed  as  described  and  the  ammonia  is  in  moderate  ex- 

1  The  volume  of  wash  water  should  not  be  too  large  :  vide  Hillebrand. 
*  The  accuracy  of  this  method  admits  of  criticism,  but  its  convenience  and  rapidity 
demand  its  insertion. 


256  PORTLAND  CEMENT 

cess.  It  is  then  allowed  to  stand  for  about  2  hours  when  it  is 
filtered  on  a  paper  or  a  Gooch  crucible,  ignited,  cooled  and 
weighed  as  Mg2P2OT. 

Method  Proposed  by  the  Committee  on  the  Uniform  Analysis  of 

Cement  and  Cement  Materials  of  the  Lehigh  Valley  Section 

of  the  American  Chemical  Society.1 

Silica. 

Weigh  out  0.5  gram  into  a  wide  platinum  dish  of  about  50  cc. 
capacity ;  add  a  very  little  water  and  break  up  lumps  with  a  glass 
rod;  add  5  cc.  hydrochloric  acid  (i-i)  and  evaporate  to  dryness 
at  a  moderate  heat,  continuing  to  heat  the  mass — not  above  200° 
C. — until  all  odor  of  acid  is  gone.  Do  not  hurry  this  baking  or 
skimp  the  time.  The  whole  success  of  the  analysis  depends  on 
thoroughness  at  this  point.  Cool ;  add  20  cc.  hydrochloric  acid 
(i-i)  ;  cover  and  boil  gently  for  ten  minutes;  add  30  cc.  water, 
raise  to  boiling,  and  filter  off  the  silica;  wash  with  hot  water  four 
or  five  times;  put  in  crucible,  ignite  (using  blast  for  10  minutes), 
and  weigh  as  SiO2. 

Iron  and  Alumina. 

Make  filtrate  alkaline  with  ammonia,  taking  care  to  add  only 
slight  excess;  add  a  few  drops  of  bromine  water  and  boil  till 
odor  of  ammonia  is  faint.  Filter  off  the  hydroxides  of  iron  and 
aluminum-,  washing  once  on  the  filter.  Dissolve  the  precipitate 
with  hot  dilute  nitric  acid,  reprecipitate  with  ammonia;  boil  five 
minutes;  filter  and  wash  the  iron  and  alumina  with  hot  water 
once ;  place  in  crucible,  ignite  carefully,  using  blast  for  5  min- 
utes, and  weigh  combined  iron  and  aluminum  oxides. 

Lime. 

Make  the  filtrate  from  the  hydroxides  alkaline  with  ammonia: 
boil ;  add  20  cc.  boiling  saturated  solution  ammonium  oxalate ; 
continue  boiling  for  five  minutes ;  let  settle  and  filter.  Wash  the 

l  This  committee  was  appointed  at  a  meeting  of  the  I^ehigh  Valley  Section  of  the 
American  Chemical  Society,  held  November  18,  1903,  and  consisted  of  Messrs.  Wm.  B. 
Newberry,  Richard  K.  Meade  and  Ernest  B.  McCready.  Their  report  was  published  in 
Cement  and  Engineering  News,  August,  1904,  and  embodies  the  methods  most  acceptable  to 
the  chemists  actively  employed  in  the  cement  industry  as  ascertained  by  correspondence 
with  these  chemists  themselves. 


THE    ANALYSIS    OF    CEMENT  257 

calcium  oxalate  thoroughly  with  hot  water  using  not  more  than 
125  cc.,  and  transfer  it  to  the  beaker  in  which  it  was  precipitated, 
spreading  the  paper  against  the  side  and  washing  down  the  pre- 
cipitate first  with  hot  water  and  then  with  dilute  sulphuric  acid 
(1-4);  remove  paper;  add  50  cc.  water,  10  cc.  cone,  sulphuric 
acid,  heat  to  incipient  boiling  and  titrate  with  permanganate,1  cal- 
culating the  CaO. 

Magnesia. 

If  the  filtrate  from  the  calcium  oxalate  exceeds  250  cc.,  acidify, 
evaporate  to  that  volume ;  cool,  and  when  cold  add  1 5  cc.  strong 
ammonia  and  with  stirring  15  cc.  stock  solution  of  sodium  hy- 
drophosphate.  Allow  to  stand  in  the  cold  six  hours  or  prefer- 
ably over  night;  filter;  wash  the  magnesium  phosphate  with  di- 
lute ammonia  (1-4  -f-  100  gms.  ammonium  nitrate  per  liter)  put 
in  crucible,  ignite  at  low  heat  and  weigh  the  magnesium  pyro- 
phosphate. 

NOTES. 

Of  the  above  schemes,  the  first  is  undoubtedly  the  more  accurate  of 
the  two.  It  does  not  seem  practicable,  however,  to  use  it  in  the  every- 
day routine  work  of  the  mill  laboratory.  It  also  requires  a  high  de- 
gree of  manipulative  skill  to  carry  out  the  additional  steps  in  its  per- 
formance. When  very  accurate  determinations  are  required,  it  will  un- 
doubtedly give  better  results  than  the  second  scheme,  provided  the 
analysis  is  skilfully  executed.  On  the  other  hand,  under  the  conditions 
usually  met  with  in  the  laboratories  of  cement  manufacturers  and  large 
users,  where  rapidity,  coupled  with  a  moderate  degree  of  accuracy  is 
required,  and  where  one  man  is  required  to  run  a  number  of  analyses 
per  day,  the  second  scheme  will  unquestionably  give  more  satisfaction, 
if  properly  carried  out.  A  combination  of  the  two  schemes  which 
will  usually  be  found  as  far  as  the  general  run  of  analysts  would  care 
to  go  towards  using  the  first  scheme,  consists  in  determining  silica  as 
directed  by  the  first  scheme,  without,  however,  purifying  the  silica  with 
hydrochloric  and  hydrofluoric  acids,  and  then  the  other  elements  by  the 
second  scheme.  This  adds  to  the  accuracy  of  the  latter  and  is  not  so 
tedious  as  the  first. 

A   good   well-made    Portland   cement   is   practically   entirely   soluble   in 
hydrochloric   acid.     Fusion,   therefore,   with    sodium   or   potassium   carbo- 
nate is  rarely  necessary.     It  is  also  objectionable,  for  when  calcium  and 
magnesium  are  precipitated,  as  oxalate  and  phosphate  respectively,   from 
1  See  "  Volumetric  determination  of  I,ime,  "  page  266. 
17 


258  PORTLAND  CEMENT 

solutions  containing  much  sodium  or  potassium  salts,  the  precipitates 
are  almost  sure  to  be  contaminated  with  alkaline  salts.  Even  much 
washing  fails  to  remove  the  impurity  from  the  precipitate.  When, 
therefore,  the  sample  of  cement  has  been  fused  directly  with  from  3 
to  5  grams  of  sodium  carbonate,  there  is  sure  to  be  this  danger  that  the 
lime  and  magnesia  precipitates  will  carry  down  some  sodium  salts,  from 
which  subsequent  washing  will  fail  to  free  them.  In  accurate  work  this 
error  can  be  eliminated  by  reprecipitation.  If  instead  of  fusing  the  sam- 
ple directly  with  five  to  ten  times  its  weight  of  sodium  carbonate,  the 
impure  silica,  separated  by  treatment  with  hydrochloric  acid,  is  fused 
with  an  equal  bulk  of  sodium  carbonate,  the  quantity  of  sodium  salts 
introduced  into  the  solution  will  be  reduced  to  one-fourth,  usually  be- 
tween i.o  and  1.5  gram  of  sodium  chloride. 

Should  the  cement  prove  to  leave  a  considerable  residue  of  silicious 
matter  on  dissolving  in  acid,  the  best  plan  will  be  to  weigh  out  a  new 
sample  and  pursue  the  following  method  suggested  by  Dr.  Porter  W. 
Shimer,  Easton,  Pa. : 

Weigh  Yz  gram  of  the  finely  ground  dried  cement  into  a  platinum 
crucible  and  mix  intimately,  by  stirring  with  a  glass  rod,  with  0.5 
gram  of  pure  dry  sodium  carbonate.  Brush  off  the  rod  into  the  cruci- 
ble with  a  camel's  hair  brush.  Cover  the  crucible  and  place  over  a  low 
flame.  Gradually  raise  the  flame  until  the  crucible  is  red  hot  and  con- 
tinue the  heating  for  five  minutes  longer ;  then  place  over  a  blast  lamp 
and  heat  five  minutes  more.  While  still  hot,  plunge  the  bottom  of  the 
crucible  half  the  way  up  into  cold  water.  This  will  loosen  the  mass. 
Drop  the  mass  into  a  casserole  or  dish  and  cover  the  latter  with  a 
watch-glass.  Pour  into  the  crucible  a  portion  of  a  mixture  of  30  cc. 
of  hot  water  and  10  cc.  of  dilute  hydrochloric  acid.  Heat  on  a  hot 
plate,  and  then  pour  into  the  dish  o-r  casserole.  Clean  out  the  crucible 
with  a  rubber-tipped  rod,  using  the  rest  of  the  acid  and  water.  The 
quantity  of  sodium  salts  introduced  into  the  solution  from  0.5  gram  of 
carbonate  is  so  small  that  possible  contamination  of  the  lime  and  mag- 
nesia precipitates  is  done  away  with.  On  heating  cement  and  sodium 
carbonate  together  in  this  proportion  no  fusion  takes  place,  only  a  sin- 
tering. 

The  above  method  of  procedure  will  be  found  useful  also  in  the  analysis 
of  Rosendale  or  Natural  cement,  hydraulic  limes,  slag  cement,  puzzolana 
and  the  so-called  "Iron-cements." 

Some  operators1  make  the  amount  of  residue  left  on  solution  with 
acid  a  test  of  the  thoroughness  with  which  the  cement  has  been  made. 
Peckham  uses  a  10  per  cent,  solution  of  hydrochloric  acid  and  5  grams 
of  cement  just  received,  making  the  solution  slowly  and  with  care. 
Blount  dissolves  the  cement  in  strong  hydrochloric  acid,  evaporates 

i  Peckham  :  J.   S.   Chem.  Ind.,  XXI,  831  and  J.  Amer.  C/iem.  Soc.,  XXVI,   1636  and 
Blount  :/.  Amer.  Chcm.  Soc.,  XXVI,  995. 


TH£    ANALYSIS    OF    CEMENT  259 

the  solution  to  dryness,  but  not  intentionally  baking  the  evaporated 
material,  redissolves  in  hydrochloric  acid,  filters,  washes,  dissolves  the 
precipitated  silica  with  sodium  carbonate  solution  and  collects,  ignites 
and  weighs  the  final  insoluble  residue. 

If  this  test  is  to  be  made  use  of  to  check  the  burning  and  proper 
grinding  and  mixing  of  the  raw  materials  the  process  of  Blount  is  more 
nearly  correct,  since  it  is  not  effected  so  much  by  the  conditions  under 
which  solution  is  effected.  The  quantity  of  silica  which  will  be  left  on 
treating  cement  with  acid  will  depend  not  only  upon  the  chemical  com- 
position of  the  cement,  but  also  upon  the  fineness  to  which  the  sample 
is  ground,  strength  of  acid,  etc.,  coarsely  ground  material  giving  much 
more  residue  than  finely  ground.  Cement  passing  a  5o-mesh  sieve,  but 
retained  by  a  100,  will  give  much  more  silica  than  that  passing  a  100- 
mesh,  but  retained  on  a  2OO-mesh,  yet  neither  has  binding  properties  in 
the  ordinary  sense  of  the  word,  so  that  the  contention  made  that  the 
silica  which  does  not  dissolve  even  though  it  may  come  from  good 
properly  burned  material,  still  comes  from  inert  particles,  and  is  there- 
fore not  in  a  form  of  active  combination,  is  not  logical  because  by 
grinding  these  inert  particles  a  little  finer  we  can  considerably  reduce 
the  silica  left  without  increasing  any  their  hydraulic  value.  Many  sili- 
cates are  also  soluble  in  acid,  which  have  no  hydraulic  properties,  such 
as  slags,  so  that  all  the  silica  which  goes  into  solution  is  not  necessarily 
combined  in  such  a  way  as  to  form  hydraulic  compounds. 

The  test  as  applied  by  Blount  does  not  seem  of  much  practical  value, 
either.  Of  course,  when  the  residue  of  uncombined  silica  is  large,  it 
shows  something  is  wrong  with  the  cement,  but  this  fact  is  usually  re- 
vealed much  more  satisfactorily  by  the  tests  for  soundness  which  prop- 
erty is  dependent  on  the  proper  combination  of  the  silica  with  the 
lime.  A  marl  containing  a  per  cent,  or  so  of  silica  in  the  form  of 
quartz  grains  would  probably  give  a  cement  containing  from  ^  to  I  per 
cent,  of  insoluble  or  uncombined  silica,  yet  if  this  quartz  had  been 
taken  into  consideration  in  proportioning  the  raw  materials,  this  ce- 
ment might  easily  be  better  than  one  which  gives  no  free  or  uncom- 
bined silica,  because  the  latter  might  be  unsound.  Also,  as  we  have  said 
before,  all  the  silica,  which  is  reported  as  combined  is  not  necessarily 
so  combined  as  to  form  Portland  cement. 

At  the  mill  itself,  there  is  little  knowledge  to  be  gained  by  the 
test  as  used  by  either  Peckham  or  Blount,  as  the  soundness  test,  coupled 
with  the  usual  determinations,  will  tell  whether  the  fault  is  due  to  care- 
less manufacture  or  improper  proportioning  of  the  raw  materials. 

Alex.  Cameron,1  in  1894,  pointed  out  the  fact  that  no  matter  how 
many  evaporations  were  made  in  determining  silica,  accurate  results 
could  not  be  obtained  unless  a  filtration  intervened  between  each  one. 

i  Chem.  News.  I,XIX,  171. 


260 


PORTLAND 


This  paper  seems  to  have  escaped  the  notice  of  most  chemists  and  was 
only  brought  to  their  knowledge  by  Dr.  W.  F.  Hillebrand,1  in  1901,  in 
a  paper  read  at  a  meeting  of  The  American  Chemical  Society,  in  Phila- 
delphia, in  December  of  that  year,  in  which  he  gave  the  results  of  his 
own  experiments  along  that  line.  It  was  in  accordance  with  his  sug- 
gestion that  the  committee  of  the  New  York  Section  of  the  Society  of 
Chemical  Industry  advised  the  double  evaporation  with  intervening 
filtration,  which  they  inserted  in  their  scheme.  There  is  no  question 
but  that  Dr.  Hillebrand  is  right  and  that  this  procedure  is  necessary 
in  very  accurate  work.  In  the  analysis  of  Portland  cement,  a  residue 
of  silica,  amounting  to  from  two  to  four  milligrams,  can  usually  be  ob- 
tained by  evaporation  of  the  nitrate  from  the  first  silica  precipitate  to 
dryness,  still  the  extra  step  is  tedious,  and  adds  considerably  to  the 
time  necessary  for  making  an  analysis.  It  is  also  true,  however,  that 
there  is  considerable  iron  and  alumina  carried  down  with  the  silica,  and 
that  these  two  errors  will  balance  each  other  to  a  great  extent,  so  that 
the  amount  of  silica  reported  is  seldom  more  than  one  or  two-tenths  of 
a  per  cent.  low.  Below  are  some  figures  upon  this. 


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1 

I 

Cement  No. 

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8 

7  oH 

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I 

19-95 

0-35 

0.38 

0.09 

20.07 

—  0.12 

2 

20.18 

0.3t 

0.42 

0.12 

10.41 

—0.23 

3 

20.46 

0-37 

0.36 

0.08 

29.53 

—  O.O7 

4 

21.12 

0.38 

0.24 

0.05 

20.03 

+0.09 

5 

21.63 

0-34 

0.32 

O.I4 

21.75 

0.12 

6 

22.45 

0.41 

0-34 

O.OI 

22.49 

—  O.O4 

Silica  is  hard  to  wash  and  retains  alkalies  tenaciously.  It  is  well 
for  the  inexperienced  operator,  until  he  finds  out  how  much  washing  is 
required,  to  test  with  silver  nitrate,  and  continue  the  operation  until 
the  washings  cease  to  react  for  chlorides. 

Silica  may  be  ignited  wet,  but  care  must  be  taken  not  to  dry  the  pre- 
cipitate too  quickly  over  the  flame,  else  the  steam  in  escaping  will  carry 
with  it  fine  particles  of  silica.  The  best  plan  is  not  to  place  the  crucible 
at  first  directly  over  the  burner,  but  instead  to  one  side  of  low  flame. 

^  Jour.  Amer.  Ckem.Soc.,  XXIV,  362. 

2  This  represents  the  silica  which  would  be  found  by  the  method  of  the  committee  of 
the  I,ehigh  Valley  Section  of  the  American  Chemical  Society. 
8  This  represents  the  silica  actually  present  in  the  sample. 


THE;  ANALYSIS  OF  CEMENT  261 

The  silica  must  be  ignited  over  a  blast  lamp  in  order  to  drive  off  the 
last  traces  of  water,  which  it  holds  most  tenaciously.  Ignition  over  a 
Bunsen  burner,  even  for  some  hours,  is  insufficient  for  complete  dehy- 
dration. The  blast  lamp  will  also  help  to  burn  off  the  last  trace  of  the 
carbon  of  the  filter-paper. 

The  purity  of  the  silica  can  easily  be  tested,  and  indeed  in  accurate 
work,  it  should  always  be  done.  After  burning  off  the  carbon,  igniting 
over  a  blast  and  accurately  weighing,  moisten  the  silica  with  dilute 
sulphuric  acid  and  then  half  fill  the  crucible  with  C.  P.  hydrofluoric 
acid.  Incline  the  crucible  on  a  tripod  over  a  burner  turned  low,  in  such 
a  way  that  the  flame  plays  under  the  upper  part  of  the  crucible.  This 
causes  a  rapid  evaporation  of  the  solution.  When  no  more  fumes  come 
from  the  crucible  move  the  burner  back  until  it  plays  upon  the  bottom 
of  the  crucible  and  raise  the  flame  until  the  crucible  is  cherry-red. 
Cool  and  weigh.  The  loss  represents  silica,  SiO2,  and  the  residue  in  the 
crucible  is  usually  alumina.  Its  weight  may  be  added  to  that  of  the  iron 
and  alumina  found  by  precipitation  with  ammonia,  or  the  residue  may 
be  dissolved  in  concentrated  hydrochloric  acid  and  added  to  the  fil- 
trate from  the  silica,  before  the  addition  of  ammonia. 

If  silica  is  to  be  purified,  however,  it  is  also  necessary,  not  only  to 
make  the  double  evaporation  with  intervening  filtration,  but  also  to 
determine  the  silica  in  the  iron  and  alumina  and  add  it  to  the  weight 
of  the  purified  silica.  Unless  this  is  done  the  silica  will  be  too  low  and 
the  iron  and  alumina  too  high. 

Alumina,  Al2Os,  is  soluble  TO  some  extent  in  a  large  excess  of  am- 
monia. If,  however,  the  excess  is  expelled  by  boiling,  the  alumina  is 
again  precipitated.  The  presence  of  ammonium  chloride  in  the  solu- 
tion greatly  aids  in  the  separation  of  alumina  by  ammonia.  The  pre- 
cipitate of  iron  and  alumina  must  be  filtered  off  promptly  since  the 
alkaline  liquid  will  absorb  carbon  dioxide  from  the  air,  forming  caf- 
cium  carbonate  which  would  be  filtered  off  with  the  iron  and  alumina. 
For  the  same  reason,  when  for  any  cause  the  filtrate  from  the  iron  and 
alumina  has  to  stand  some  days,  it  should  be  acidified  with  hydrochloric 
acid  before  setting  aside.  This  is  necessary  when  the  calcium  is  to  be 
determined  volumetrically,  and  it  saves  trouble  elsewhere,  since  the 
deposit  of  calcium  carbonate  forms  as  a  crust  on  the  sides  and  bottom 
of  the  beaker,  and  is  very  difficult  to  remove,  without  solution  and  re- 
precipitation. 

To  avoid  time  lost  in  boiling  off  a  large  excess  of  ammonia,  only  a 
very  slight  excess  of  this  reagent  should  be  added.  The  bottle  shown  in 
Fig.  81  will  be  found  very  useful  in  ammonia  precipitations,  as  the 
addition  can  be  made  drop  by  drop,  if  desired,  and  the  quantity  added 
regulated  so  as  to  give  the  liquid  only  a  faint  odor  of  ammonia. 

Magnesium  hydroxide,  Mg(OH)2,  is  not  completely  soluble  in  am- 
monia. The  precipitate  is,  however,  readily  soluble  in  ammonia  solu- 


262 


PORTLAND  CEMENT 


tions,  containing  sufficient  ammonium  chloride.  The  precipitation  of 
the  magnesia  along  with  the  iron  and  alumina  is  insured  against  by  the 
formation  of  ammonium  chloride  which  takes  place  before  the  iron  and 
alumina  are  precipitated,  on  adding  ammonia  to  the  hydrochloric  acid 
solution.  If  preferable  the  operator  can  be  on  the  safe  side  by  adding 
half  a  gram  of  the  salt  itself  (ammonium  chloride)  to  the  filtrate  from 
the  silica  before  precipitating  the  iron  and  alumina.  The  presence  of 
ammonium  chloride  is  also  necessary  for  the  complete  precipitation  of 
the  alumina. 


Fig.  81.— Apparatus  for  ammonia  precipitation. 

The  precipitate  of  iron  and  alumina  always  contains  more  or  less 
lime  and  magnesia,  from  which  long  washing  fails  to  free  it.  Solution 
and  reprecipitation  are,  therefore,  necessary  to  get  around  the  diffi- 
culty. The  precipitate  is  very  apt  to  contain  traces  of  silica  also. 
Some  of  this  comes  from  the  action  of  the  ammonia  on  the  reagent 
bottle  in  which  it  is  kept,  some  from  the  action  of  the  alkaline  liquid  on 
the  beaker  in  which  the  precipitation  was  made,  and  some  which  failed 
to  be  separated  by  evaporation  in  the  proper  place  is  also  carried  down 
here.  Since  the  impurity  usually  present  in  the  silica  is  alumina  and 
that  in  the  alumina  is  silica,  the  two  sources  of  error  tend  to  balance 
each  other.  If  desired  the  weighed  precipitate  of  ferric  oxide  and 
alumina  can  be  dissolved  by  fusion  with  potassium  bisulphate  for  some 
hours,  the  fused  mass  dissolved  in  water,  a  few  drops  of  sulphuric 
acid  added  and  the  solution  evaporated  until  fumes  come  off  in  quan- 


THE;  ANALYSIS  OF  CEMENT  263 

tity.  The  residue  is  then  collected  after  cooling  and  diluting  the  so- 
lution,1 and  weighed  as  SiOz. 

Ammonia  water  takes  up  silica  rapidly  from  the  glass  container, 
hence  when  accurate  work  is  desired,  and  purification  of  silica  and 
alumina  are  to  be  undertaken;  it  is  necessary  to  redistill  the  am- 
monia over  lime.  This  should  be  done  every  week  or  two  at  least. 
Even  for  technical  work  it  is  not  a  bad  plan,  as  there  is  no  telling 
how  long  the  ammonia  has  stood  on  some  dealer's  shelves.  The  still 
may  be  kept  set  up  in  a  corner  of  the  hood  and  the  operation  con- 
ducted by  the  laboratory  boy.  By  using  redistilled  ammonia  it  is  pos- 
sible to  do  away  with  the  second  precipitation  of  the  iron  and  alumina, 
which  is  made  necessary  by  the  presence  of  ammonium  carbonate  in  the 
ammonia  water,  as  this  carbonate  precipitates  some  calcium  carbonate 
along  with  the  alumina.  Of  late  years  the  author  has  been  able  to  pur- 
chase ammonia  water  contained  in  wax  bottles.  This  of  course  has  had 
no  chance  to  take  up  silica  and  the  trouble  of  redistilling  is  saved. 

The  precipitate  of  iron  and  alumina  is  troublesome  to  wash,  and  un- 
less it  is  freed  from  chlorides,  some  loss  of  iron,  by  volatilization  as 
ferric  chloride,  will  result  when  the  precipitate  is  ignited.  In  order 
to  avoid  this  tedious  washing,  the  writer  has  always  followed  the  plan 
of  dissolving  the  first  precipitate  in  nitric  acid,  thus  avoiding  the  pres- 
ence of  chlorides  in  the  second  precipitate  and  doing  way  with  the  ted- 
ious washing.  When  this  is  done  only  enough  washing  is  necessary  to 
collect  the  precipitate  in  the  point  of  the  filter.  This  plan  is  suggested 
in  the  method  of  the  Lehigh  Valley  Committee. 

Calcium  oxalate  may  be  washed  with  hot  water.  Some  chemists  pre- 
fer to  add  a  little  ammonia  to  the  wash  water,  but  to  the  author  this 
seems  unnecessary.  The  precipitate  should  always  be  formed  in  a 
boiling  ammoniacal  solution,  with  stirring,  and  allowed  to  settle  before 
filtering.  Some  chemists  heat  the  ammonium  oxalate  solution  also  to 
boiling  before  adding  to  the  boiling  solution  containing  the  calcium. 
Sufficient  ammonium  oxalate  should  always  be  added  to  convert  all  the 
magnesium  present  as  well  as  the  calcium  to  oxalate,  else  the  precipi- 
tation of  the  calcium  will  be  incomplete.  Nothing  is  gained  by  allowing 
the  lime  more  than  15  or  20  minutes  to  settle. 

Magnesium  oxalate  is  not  very  soluble  and  if  magnesia  is  present  in 
large  amount  will  be  precipitated  with  the  lime.  On  the  other  hand, 
calcium  oxalate  is  slightly  soluble  in  hot  water.  As  cement  contains 
such  a  small  percentage  of  magnesia  the  quantity  carried  down  with  the 
lime  is  usually  less  than  o.i  per  cent.,  and  as  the  quantity  of  calcium 
oxalate  which  goes  into  solution  is  precipitated  with  the  magnesia,  the 
two  errors  tend  to  balance  each  other.  The  factors  entering  into  a  clean 
separation  of  lime  and  magnesia  are  that  there  must  be  an  excess  of 
ammonium  oxalate  and  that  the  solution  should  measure  at  least  300  cc. 

i  Hillebrand./owr  Amer.  Chem.  Soc.  XXIV.,  369. 


264  PORTLAND 

Directions  for  making  the  solution  for  determining  lime  volumetri- 
cally  and  for  carrying  out  the  process  will  be  found  on  page  185.  The 
volumetric  determination  is  very  accurate  and  under  ordinary  techni- 
cal conditions,  when  many  analyses  are  made  every  day,  will  prove  as 
trustworthy  as  the  gravimetric.  When  an  occasional  determination  only 
is  made  the  latter  will  prove  more  useful. 

Calcium  oxalate  on  ignition  over  a  burner  to  very  faint  redness  changes 
to  calcium  carbonate.  If  the  heating  is  increased  and  the  blast  is  used 
calcium  oxide  is  formed.  Instead  of  weighing  as  the  oxide  some  chem- 
ists prefer  to  weigh  as  a  sulphate.  To  do  this,1  dry  the  precipitate  per- 
fectly, detach  it  as  far  as  possible  from  the  filter  to  a  piece  of  black 
glazed  paper.  Burn  the  filter-paper  in  a  weighed  platinum  crucible,  and 
when  all  carbonaceous  matter  is  burned,  brush  the  precipitate  into  the 
crucible  from  the  glazed  paper.  Drop  concentrated  sulphuric  acid  on 
the  precipitate  till  it  is  well  moistened,  avoiding  an  excess,  and  heat  th« 
crucible  under  a  hood  cautiously,  from  a  burner  held  in  the  hand,  until 
the  swelling  of  the  mass  subsides  and  the  excess  of  sulphuric  acid  has 
been  driven  off,  as  shown  by  the  disappearance  of  the  white  fumes  com- 
ing from  the  crucible.  Then  heat  for  five  minutes  to  a  cherry-red  heat, 
but  do  not  use  the  blast.  Cool  and  weigh  as  calcium  sulphate,  which 
multiplied  by  0.41195  gives  the  equivalent  of  lime  CaO. 

Mr.  W.  H.  Hess  uses  the  following  method1  for  converting  the  cal- 
cium oxalate  to  calcium  sulphate.  After  burning  off  all  the  carbon  of 
the  filter-paper,  the  crucible  is  allowed  to  cool  partly,  when  a  portion  of 
chemically  pure  dry  ammonium  nitrate,  approximately  equal  in  bulk  to 
the  lime  in  the  crucible,  and  about  twice  as  much  chemically  pure  fused 
ammonium  sulphate  are  added,  A  tight-fitting  cover  is  now  placed  on 
the  platinum  crucible  and  then  gentle  heat  is  applied.  Mr.  Hess  found 
it  very  convenient  to  incline  the  crucible  at  an  angle  of  30°,  allowing 
the  tip  of  the  crucible  cover  to  project  outward,  and  then  apply  the 
flame  to  the  tip  of  the  cover,  gradually  bringing  the  flame  under  the 
crucible  as  the  reaction  grows  less  and  less  violent.  The  reaction  is 
complete  when  fumes  of  ammonia  salts  are  no  longer  driven  off.  In- 
tense ignition  is  unnecessary  and  is  to  be  avoided.  The  crucible  should 
be  weighed  with  its  cover. 

The  evaporation  of  the  filtrate  from  the  lime  may  be  rapidly  carried 
out,  in  a  large  porcelain  dish,  in  the  following  manner:  Place  a  piece 
of  wire  gauze  on  a  tripod  and  in  the  center  of  this,  lay  a  disk  of  as- 
bestos paper,  the  size  of  a  silver  dollar.  Now  set  the  dish  on  the  gauze 
and  place  a  Bunsen  burner,  with  its  flame  turned  low,  so  that  the  latter 
comes  under  the  asbestos.  The  solution  will  then  evaporate  rapidly,  and 
yet  without  ebullition,  or  loss  by  spurting. 

Magnesium   pyrophosphate    is   quite   soluble   in   hot   water,   less    so   in 

1  I,ord,   "Notes  on  Metallurgical  Analysis,"  p.  n. 
*  Jour.  Amer.  Chem.  Soc.,  32,  477. 


THE    ANALYSIS    OF    CEMENT 


cold  water,  and  practically  insoluble  in  water  rendered  strongly  am- 
moniacal.  It  should  be  washed,  therefore,  with  a  mixture  of  water  and 
ammonia.  Some  chemists  use  no  ammonium  nitrate  in  their  washing 
fluid,  and  mix  in  proportions  varying  from  ten  to  three  parts  water  for 
one  part  of  ammonia.  It  is  a  difficult  precipitate  to  ignite  perfectly 
white,  but  the  blast  lamp  should  never  be  used  in  the  attempt  to  make  it 
so,  as  destruction  of  the  platinum  crucible  might  follow.  The  precipitate 
may  be  ignited  wet  if  a  low  flame  is  used  at  first. 

A  Gooch  crucible  may  be  used  in  place  of  a  filter-paper,  although  it 
is  much  less  convenient.  It  consists  of  a  flat-bottomed,  perforated  cruci- 
ble provided  with  a  cap  (Fig.  82).  The  perforated  crucible  is  placed 
in  one  end  of  a  piece  of  soft  rubber  tubing  of  large  bore,  the  other 
end  of  which  is  stretched  over  a  small  funnel  passing  into  a  flask 
through  a  rubber  stopper  (Fig.  83).  The  flask  is  connected  with  the 
filter-pump.  To  prepare  the  filter,  pour  a  little  prepared  asbestos  (puri- 
fied by  washing  with  hot  concentrated  hydrochloric  acid)  suspended  in 
water  into  the  crucible  and  attach  the  suction  to  the  flask.  The  asbestos 
at  once  forms  a  thick  felt  over  the  bottom  of  the  crucible,  which  by 
using  the  suction  may  be  readily  washed  with  water.  After  washing, 
suck  dry  as  possible  with  the  pump,  remove  from  the  funnel,  detach  any 


Fig.  82. — Gooch  crucible. 


Fig.  83.— Gooch  crucible  in  use. 


pieces  of  asbestos  that  may  be  on  the  outside  of  the  bottom  of  the 
crucible,  cap,  ignite,  and  weigh.  Remove  the  cap,  attach  to  the  funnel 
as  before,  apply  the  suction  and  pour  the  liquid  to  be  filtered  through 
the  crucible,  wash,  cap,  dry,  if  necessary,  ignite  and  weigh  as  before. 
The  crucible  and  cap  may  be  purchased  from  dealers  in  platinum  or 
chemical  ware. 

The  use  of  platinum  dishes  is  recommended  for  the  solution  and 
evaporation  of  the  sample  because  platinum  is  a  much  better  conductor 
of  heat  than  porcelain  and  glass,  and  consequently  evaporations  can  be 
carried  out  much  more  rapidly  in  them  than  in  anything  else.  Silica  also 
sticks  to  porcelain  and  even  to  some  extent  to  glass  and  it  is  impossible 


266  PORTLAND  CEMENT 

to  remove  it  all  from  glass  or  porcelain  dishes  by  rubbing.  It  does  not 
stick  to  platinum  dishes,  however.  With  silica  determinations  made  in 
anything  but  platinum,  results  are  therefore  too  low.  If  the  former 
ware  must  be  used.  The  silica  which  sticks  should  be  dissolved  in 
ammonia  water  and  reprecipitated  by  acid  and  added  to  the  main  body 
of  the  silica  on  the  paper.  There  is  also  no  danger  of  contaminating  the 
analysis  with  silica  from  the  dish  when  platinum  is  used. 

Crucibles  in  which  silica  has  been  ignited  may  be  most  conveniently 
cleaned  by  boiling  in  them  a  little  hydrofluoric  acid.  Crucibles  used 
to  ignite  iron  and  alumina  are  best  cleansed  by  boiling  in  them  dilute 
(i-i)  hydrochloric  acid,  while  those  used  for  barium  sulphate  can  be 
cleaned  by  boiling  in  them  a  little  hydrofluoric  acid.  Ignited  magnesium 
pyrophosphate  may  be  readily  removed  from  platinum  or  porcelain  cruci- 
bles by  placing  the  latter  in  a  beaker  of  ten  per  cent,  hydrochloric  acid 
and  boiling.  The  dilute  acid  in  this  case  will  do  the  work  when  strong 
acid  will  fail.  No  appreciable  loss  in  weight  of  the  crucible  will  be  oc- 
casioned by  any  of  the  above  treatments. 

VOLUMETRIC  DETERMINATION  OF  LIME. 

Preparation  of  the  Standard  Permanganate. 

Dissolve  the  quantity  of  pure  crystallized  potassium  permanga- 
nate shown  in  the  table  below,  in  the  desired  amount  of  water, 
using  a  balance  accurate  to  at  least  0.5  per  cent,  of  the  weight  of 
permanganate  to  be  taken,  and  measuring  the  water  with  a  grad- 
uated flask.  In  this  way,  a  solution  can  be  made  of  sufficiently 
near  the  correct  strength  for  the  use  of  the  table  in  the  appendix. 

TABLE  XVIII. — FOR  PREPARING  STANDARD  PERMANGANATE  OF 
APPROXIMATELY  THB  STRENGTH  i  cc.  =  0.005  GRAM  CaO. 

5.64  grams  KMnO4  to     i  liter  of  water 

11.28  '•  "  "     2  "  "       " 

16.92  "  "  "3  "  " 

22.56  "  "  "     4  "  " 

28.20  "  "  "     5  "  " 

33.84  "  "  "     6  "  "        " 

39.48  •'  "  "     7  "  "       " 

45.12  "  "  "     8  "  " 

50.76  "  "  "     9  "  "       " 

56.40  "  "  "  10  "  " 

Use  a  balance  accurate  to  at  least  0.5  per  cent,  of  the  weight 
of  KMnO4  to  be  taken  and  measure  the  water  with  a  graduated 
flask. 


) 
TH£    ANALYSIS    OF    CEMENT  267 

The  simplest  way  to  make  the  solution,  is  to  weigh  out  the 
permanganate  and  place  in  the  bottle  with  the  water,  some  week 
or  ten  days  before  the  solution  is  to  be  standardized.  The  con- 
tents of  the  bottle,  which  is  kept  in  a  dark  place,  is  shaken  every 
now  and  then  for  the  first  two  or  three  days.  When  the  solution 
is  needed,  it  is  siphoned  off  into  another  bottle,  leaving  about  an 
inch  of  solution  in  the  old  bottle.  A  glass  siphon  is  used  and  its 
end  should  not  extend  nearer  than  an  inch  from  the  bottom  of 
the  bottle.  The  solution  in  the  new  bottle  is  now  shaken  and 
standardized.  The  writer  in  his  laboratory  uses  eight  liter  (2 
gallon  bottles)  and  this  quantity  of  permanganate  will  last  him 
from  two  or  three  weeks.  The  solution  should  be  standardized 
every  week.  It  will  be  found  more  convenient  to  make  the  solu- 
tion as  above  and  standardize- «ver-y--  week,  than  to  attempt  to 
make  a  solution  which  will  not  change,  by  boiling  and  filtering 
as  directed  by  Morse.1 

The  permanganate  solution  should  be  kept  in  a  dark  place. 
Fig.  74  shows  the  arrangement  for  storing  and  using  the  per- 
manganate adopted  by  the  writer.2 

Standardising  the  Permanganate. 

To  standardize  the  permanganate,  weigh  into  a  400  cc.  beaker 
0.5  gram  of  powdered  calcite;  add  100  cc.  of  water  and  10  cc. 
of  hydrochloric  acid,  cover  with  a  watch-glass  and  boil  until  all 
carbon  dioxide  is  expelled.  When  completely  dissolved,  dilute 
to  the  usual  volume  in  which  the  lime  precipitation  is  made  in  an 
analysis,  and  make  alkaline  with  ammonia.  Add  20  cc.  of  a 
boiling  saturated  solution  of  ammonium  oxalate,  continue  boil- 
ing and  stirring  for  a  few  minutes,  let  settle,  filter  and  wash  thor- 
oughly with  hot  water  using  not  more  than  125  cc.  of  the  liquid. 
Transfer  the  filter  and  precipitate  to  the  beaker  in  which  the  pre- 
cipitation was  made,  spreading  the  paper  against  the  side  and 
washing  down  the  precipitate  first  with  hot  water  and  then  with 
dilute  sulphuric  acid  (1-4).  Remove  the  paper,  add  50  cc.  of 
water  and  10  cc.  concentrated  sulphuric  acid,  heat  in  incipient 

1  Amer.  Ckem.Jout.,XVlII,  401. 

2  Chemical  Engineer,  I.,  288. 


268 


PORTLAND  CEMENT 


boiling  and  titrate  with  permanganate.  The  factor  for  lime, 
CaO,  is  found  by  dividing  0.56  by  the  number  of  cubic  centi- 
meters of  permanganate  taken  and  for  calcium  carbonate,  CaCO3, 
by  dividing  100  by  the  number. 

The  above  method  is  that  recommended  by  the  Committee  of 


Fig.  84. — Table  for  titrations. 


the  Lehigh  Valley  Section  of  the  American  Chemical  Society  on 
the  Uniform  Analysis  of  Cement  and  Cement  Materials.  Some 
operators  prefer  to  use  ferrous  ammonium  sulphate  for  stand- 
ardizing. The  usual  method  of  using  this  is  as  follows : 


THE   ANALYSIS    OF    CEMENT  269 

Weigh  into  each  of  two  beakers  1.4  grams  of  pure  crystallized 
ferrous  ammonium  sulphate,  add  cold  water,  allow  the  salt  to 
completely  dissolve  without  stirring  and  then  add  10  cc.  of 
dilute  sulphuric  acid.  Stir  and  run  in  the  permanganate  from  a 
burette  until  the  color  of  the  solution  in  the  beaker  just  changes 
to  pink.  The  weight  of  the  double  salt  used  divided  by  14,  and 
then  by  the  number  of  cubic  centimeters  of  permanganate  re- 
quired, will  give  the  lime,  CaO,  value  per  cubic  centimeter,  for 
the  permanganate.  The  duplicate  titrations  should  check  closely ; 
if  not,  another  pair  should  be  run.  For  other  methods  of  stand- 
ardizing the  permanganate  solution  see  "Determination  or  Ferric 
Oxide." 

The  writer  has  lately  used  sodium  oxalate  prepared  as  di- 
rected by  Sorensen  for  standardizing  permanganate  and  found 
it  both  convenient  and  accurate.  Theoretically,  0.6697  grams 
of  this  salt  are  equivalent  to  0.5  gram  of  calcium  carbonate.  In 
practice  the  writer  has  usually  found  slightly  more  required  and 
prefers  therefore  to  determine  the  exact  amount  by  comparing 
it  with  calcite  or  standard  sample  of  cement  or  limestone.  Thus 
if  0.5  gram  of  calcite  requires  56.5  cc.  of  permanganate  and 
0.6700  gram  of  sodium  oxalate  56.4  cc.  Then  0.6711  grams  of 
sodium  oxalate  are  used  for  standardizing  thereafter.  In  use, 
the  salt  is  dissolved  in  water,  10  cc.  of  dilute  (i  :  i)  sulphuric 
acid  added,  the  solution  heated  to  60°  C.  and  titrated  with  the 
permanganate  to  be  standardized. 

The  Determination. 

Directions  for  determining  the  lime  volumetrically  are  given 
on  page  174. 

Notes. 

The  method  depends  upon  the  reaction  between  oxalic  acid  and  po- 
tassium permanganate. 

5H2C2O4  +  2KMnO4  +  3H2SO4  =  ioCO2  +  K2SO4  +  2MnSO6  +8H2O 
The  reaction  between  iron  and  permanganate  is 

ioFeSO4  +  2KMnO4  +  8H2SO4  =  5Fe2(SO4)5  -f  2MnSO4  -f  K2SO4  +  8H2O. 
Hence  5  molecules  H2C2O4  =  2  mols.     KMnO4  =  10  mols.     FeSO4  or  5 
mols.     H2C2O4  (=  5  mols.  CaO)  =  10  mols.  FeSO4  (  =  10  atoms  Fe). 


PORTLAND 

Then  5  mols.  CaO  =  10  atoms  Fe,  and  5  (40  -f  16)  CaO  =  10  X  56  Fe,  or 
280  CaO  =  560  Fe. 
Hence,  CaO  :   Fe    : :  280   :  560,   from  which  CaO  =    ^    Fe  or  — - — Fe. 

So  the  iron  value  of  any  permanganate  solution  divided  by  2  will 
give  its  lime  value. 

The  titration  with  permanganate  must  be  made  with  a  hot  solution, 
between  60°  and  70°  C.  In  the  scheme  given,  the  solution  is  heated 
by  the  action  with  the  strong  sulphuric  acid,  added  just  before  titration. 

C'alcite  in  the  form  of  Iceland  Spar  can  be  obtained  of  great  purity, 
and  may  be  generally  taken  as  100  per  cent.  CaCOs.  In  purchasing  a 
new  lot  it  should  be  specified  that  the  purest  grade  is  wanted  "for 
standardizing."  On  receipt  it  should  be  powdered  to  pass  a  loo-mesh 
sieve  and  kept  in  a  glass  stoppered  bottle.  From  this  a  small  portion 
should  be  taken  and  placed  in  an  ounce  wide  mouth  bottle,  provided 
with  either  a  glass  or  rubber  stopper.  This  small  sample  should  be  dried 
at  from  100-110°  G.,  and -on -removal— from-  the-  drying  oven  kept  tightly 
stoppered.  The  calcite  should  then  be  checked  by  a  careful  analysis  for 
silica,  iron  oxide  and  alumina  and  the  lime  determined  gravimetrically 
as  on  page  255.  A  blank  should  be  run  at  the  same  time;  that  is,  a  dish 
is  selected  and  acid  added  to  it  just  as  if  it  contained  a  sample,  etc. 
The  small  residues  found  after  each  step  should  be  deducted  from  those 
found  on  analysis  of  the  calcite.  The  sample  used  in  the  writer's  lab- 
oratory gave  less  than  o.i  per  cent,  impurities  when  treated  in  this 
manner.  The  small  sample  of  calcite  should  be  dried  after  the  bottle 
has  been  opened  for  five  or  six  determinations,  as  it  will  take  up  some 
moisture  from  the  air. 

Rapid  Determination  of  Lime  Without  Separation  of  Silica,  Etc.1 

Weigh  0.5  gram  of  cement  into  a  dry  500  cc.  beaker  and  add, 
with  constant  stirring,  20  cc.  of  cold  water.  Break  up  the  lumps 
and  when  all  the  sample  is  in  suspension,  except  the  heavier  par- 
ticles, add  20  cc.  of  dilute  (i-i)  hydrochloric  acid  and  heat  until 
solution  is  complete.  This  usually  takes  5  or  6  minutes.  Heat 
to  boiling  and  add  dilute  ammonia  (0.96  sp.  gr.)  carefully  to  the 
solution  of  the  sample  until  a  slight  permanent  precipitate  forms. 
Heat  to  boiling  and  add  10  cc.  of  a  10  per  cent,  solution  of  oxalic 
acid.  Stir  until  the  oxide  of  iron  and  alumina  are  entirely 
dissolved  and  only  a  slight  precipitate  of  calcium  oxalate  re- 
mains. Now  add  200  cc.  of  boiling  water  and  sufficient  (20  cc.) 
saturated  solution  of  ammonium  oxalate  to  precipitate  the  lime. 
Boil  and  stir  for  a  few  moments,  remove  from  the  heat,  allow 

1  Chemical  Engineer,  I.,  21. 


THE    ANALYSIS    OF    CEMENT 

the  precipitate  to  settle  and  filter  on  an  1 1  cm.  filter.  Wash  the 
precipitate  and  paper  ten  times  with  hot  water  using  not  more 
than  10  or  15  cc.  of  water  each  time.  Remove  the  filter  from 
the  funnel,  open  and  lay  against  the  sides  of  the  beaker  in  which 
the  precipitation  was  made,  wash  from  the  paper  into  the  beaker 
with  hot  water,  add  dilute  sulphuric  acid,  fold  the  paper  over 
and  allow  to  remain  against  the  walls  of  the  beaker.  Heat  to 
80°  C.  and  titrate  with  standard  permanganate  until  a  pink  color 
is  obtained,  now  drop  in  the  filter-paper,  stir  until  the  color  is 
discharged  and  finish  the  titration  carefully  drop  by  drop. 

NOTES. 

The  above  method  for  the  determination  of  lime  is  dependent  on  the 
fact  that  lime  can  be  completely  precipitated  as  oxalate  in  solutions 
containing  free  oxalic  ^cid,  white  iron,  "alumina  and  magnesia  are  not. 
The  method  as  outlined  above  was  worked  out  by  the  writer  some  years 
ago  and  has  been  in  constant  use  in  the  laboratories  of  many  large 
cement  companies  since  that  time,  giving  entire  satisfaction. 

The  oxalic  acid  method  is  much  more  accurate  than  the  one  sometimes 
used  of  precipitating  the  iron  and  alumina  by  ammonia  and  then  with- 
out filtration  throwing  down  the  lime  as  oxalate  in  the  same  solution, 
since  in  the  latter  method  some  of  the  lime  is  thrown  down  as  carbo- 
nate and  hence  not  found  by  the  permanganate.  It  is  just  as  rapid  as 
the  above  because  the  only  extra  step  is  the  addition  of  10  cc.  of  oxalic 
acid  solution  which  is  more  than  made  up  for  by  the  more  rapid  nitra- 
tion due  partly  to  the  fine  granular  precipitate  of  calcium  oxalate  ob- 
tained and  also  to  this  not  being  contaminated  by  the  flocculent  alumina 
precipitate. 

The  oxalic  acid  method  is  just  as  accurate  as  the  longer  one  of  sepa- 
rating the  silica,  iron,  and  alumina  from  the  solution,  before  pre- 
cipitating the  lime.  Indeed — unless  the  iron  and  alumina  are  sepa- 
rated by  double  precipitation  it  is  the  more  accurate  of  the  two. 

A  determination  can  be  made  by  the  above  method  in  from  25  to  30 
minutes,  of  which  10  or  15  are  required  for  the  lime  to  settle.  The 
ammonia  must  not  be  added  in  very  large  excess  and  to  guard  against 
this  the  addition  can  best  be  made  from  the  bottle  shown  in  Fig.  81, 
on  page  262. 

DETERMINATION  OF  FERRIC  OXIDE. 

By    Titration    with    Potassium    Permanganate.      (Marguerite's 

Method.) 

Standard  Potassium  Permanganate. 
Dissolve  1.975  grams  of  pure  crystallized  potassium  permanga- 


272  PORTLAND  CEMENT 

nate  in  100  cc.  of  water,  boil  and  allow  to  stand  all  night.  In  the 
morning  filter  through  asbestos  into  a  bottle  and  dilute  to  I  liter. 
To  test,  or  standardize,  the  solution,  weigh  into  each  of  two  beak- 
ers 0.4900  gram  of  pure  ferrous  ammonium  sulphate,  equivalent 
to  o.i  gram  of  ferric  oxide,  Fe2O3.  Dissolve  in  50  cc.  of  water, 
without  heating,  add  10  cc.  of  dilute  sulphuric  acid  and  run  in 
the  permanganate  from  a  burette  until  the  color  of  the  solution 
in  the  beaker  just  begins  to  turn  pinkish.  Take  the  reading  of 
the  burette  and  then  add  another  drop,  which  should  cause  the 
solution  to  become  decidedly  pinkish.  Divide  the  weigfit  of  ferric 
oxide  (o.i  gram)  equivalent  to  the  weight  of  ferrous  ammonium 
sulphate  taken  for  the  titration  (0.49  gram)  by  the  number  of 
cubic  centimeters  of  permanganate  required;  the  result  will  give 
the  ferric  oxide  equivalent  to  I  cc.  of  the  permanganate. 

To  use  iron  wire  in  standardizing,  clean  two  pieces  of  fine  iron 
wire,  weighing  o.i  gram  each,  by  rubbing  first  between  emery 
paper  and  then  with  a  cloth.  Coil  around  a  lead  pencil  and  weigh 


Fig.  85.— Stopper  and  valve  for  iron  reductions. 

each  coil.  Put  30  cc.  of  dilute  sulphuric  acid  in  a  strong  gas 
bottle  provided  with  a  perforated  stopper  through  which  passes 
a  perfect  fitting  glass  tube  with  a  hole  blown  in  its  side  (Fig. 
75).  Heat  the  acid  to  boiling  and  drop  in  a  coil  of  wire.  When 
triQ  solution  of  the  latter  is  complete,  remove  the  bottle  from  the 
source  of  heat  and,  after  closing  the  opening  by  pushing  the  per- 
forated glass  tube  down  until  its  opening  is  closed  by  the  stopper, 
allow  the  gas  bottle  to  cool.  When  cold  titrate  the  solution  with 
the  permanganate  solution  as  above.  Multiply  the  weight  of 
the  iron  wire  by  0.003  and  deduct  the  result  from  the  original 
weight  for  impurities.  Multiply  the  corrected  weight  by  1.4286, 
or  divide  by  0.7,  and  divide  by  the  number  of  cubic  centimeters 
of  permanganate  required.  The  result  will  be  the  ferric  oxide 


THE)    ANALYSIS    OF    CEMENT  2/3 

equivalent  of  I  cc.  of  the  standard  potassium  permanganate.  Re- 
peat the  test  with  the  other  weighed  coil  of  iron  wire.  The 
values  for  each  cubic  centimeter  of  permanganate  by  the  two 
titrations  should  agree  closely.  Yet  another  way  is  to  dissolve 
the  iron  wire  in  15  cc.  of  dilute  sulphuric  acid  in  a  beaker,  cool, 
dilute,  pass  through  the  reductor,  described  on  page  275,  and 
titrate  with  the  permanganate,  calculating  the  results  as  above. 

The  Determination. 

The  Committee  on  Uniformity  in  Analysis  of  Materials  for  the 
Portland  Cement  Industry,  of  the  New  York  Section  of  the  So- 
ciety of  Chemical  Industry,  recommend  that  the  determination 
of  ferric  iron  be  conducted  on  the  ignited  precipitate  of  ferric 
oxide  and  alumina,  after  weighing,  in  the  following  manner : 

The  combined  iron  and  aluminum  oxides  are  fused  in  a  plati- 
num crucible  at  a  very  low  temperature  with  about  3  to  4  grams 
of  KHSO4,  or,  better,  NaHSO4,  the  melt  taken  up  with  so  much 
dilute  H2SO4  that  there  shall  be  no  less  than  5  grams  absolute 
acid  and  enough  water  to  effect  solution  on  heating.  The  solu- 
tion is  then  evaporated  and  eventually  heated  till  acid  fumes 
come  off  copiously.  After  cooling  and  redissolving  in  water  the 
small  amount  of  silica  is  filtered  out,  weighed,  and  corrected  by 
HFl  and  HoSC^.1  The  filtrate  is  reduced  by  zinc,  or  preferably 
by  hydrogen  sulphide,  boiling  out  the  excess  of  the  latter  after- 
wards whilst  passing  CO2  through  the  flask,  and  titrated  with 
permanganate.2  The  strength  of  the  permanganate  solution 
should  not  be  greater  than  0.0040  gr.  Fe2O3  per  cc. 

The  Committee  appointed  by  the  Lehigh  Valley  Section  of  the 
American  Chemical  Society  direct  also  that  the  determination 
shall  be  carried  out  on  the  precipitate  of  oxide  of  iron  and  alum- 
ina. Their  method  differs  from  the  above  chiefly  in  the  manner 
of  reduction,  and  is  as  follows: 

Add  four  grams  acid  potassium1  sulphate  to  the  crucible  con- 

1  This  correction  of  A12O3  Fe2O3  for  silica  should  not  be  made  when  the  HFl  correc- 
tion of  the  main  silica  has  been  omitted,  unless  that  silica  was  obtained  by  only  one  evap- 
oration and  nitration.     After  two  evaporations  and  filtrations  i  to  2  mg,  of  SiO2  are  still 
to  be  found  with  the  A12O3  Fe2O3. 

2  In  this  way  only  is  the  influence  of  titanium  to  be  avoided  and  a  correct  result 
obtained  from  iron. 

18 


274  PORTLAND  CEMENT 

taining  the  ignited  oxides  of  iron  and  alumina,  and  fuse  at  a  very 
low  heat  until  oxides  are  wholly  dissolved — twenty  minutes  at 
least;  cool;  place  crucible  and  cover  in  small  beaker  with  50  cc. 
water;  add  15  cc.  dilute  sulphuric  acid  (1-4)  ;  cover  and  digest 
at  nearly  boiling  until  melt  is  dissolved;  remove  crucible  and 
cover,  rinsing  them  carefully.  Cool  the  solution  and  add  10 
grams  powdered  C.  P.  zinc,  No.  20.  Let  stand  one  hour,  decant 
the  liquid  into  a  larger  beaker,  washing  the  zinc  twice  by  de- 
cantation,  and  titrate  at  once  with  permanganate.  Calculate  the 
Fe2O3  and  determine  the  A12O3  by  difference.  Test  Zn,  etc.,  by 
a  blank  and  deduct. 

NOTES. 

Ferrous  salts  are  oxidized  by  potassium  permanganate  in  solutions 
containing  free  acid  to  ferric  salts  according  to  the  reaction, 

ioFeSO4  +  2KMnO4-f  8H2SO4  =  5Fe2  (SO4)3  +  K2SO4  -f  2  MnSO4  +  SH2O. 
Potassium  permanganate  does  not  give  trustworthy  results  in  the  pres- 
ence of  free  hydrochloric  acid. 

If  the  permanganate  is  prepared  as  directed  above  it  is  not  changed 
very  rapidly,  provided  it  is  kept  in  a  dark  place.  It  is  well  to  standard- 
ize it  occasionally,  however. 

To  reduce  the  iron  with  hydrogen  sulphide,  place  the  solution  into  a 
flask  and  add  to  the  solution  one-tenth  its  volume  o<f  sulphuric  acid  and 
25  cc.  of  strong  hydrogen  sulphide  water.  Heat  to  boiling.  Now  stopper 
the  flask  with  a  rubber  stopper  having  two  perforations  through  which 
two  tubes  pass.  One  tube  should  reach  nearly  to  the  bottom  of  the  flask 
and  the  other  just  inside  the  stopper.  Boil  the  solution  until  all  hydrogen 
sulphide  is  expelled,  passing  carbon  dioxide  through  the  flask  all  the 
while,  bringing  it  in  through  the  long  tube  and  out  through  the  short 
one.  The  expulsion  of  the  hydrogen  sulphide  may  be  tested  by  holding  a 
piece  of  filter-paper  moistened  with  lead  acetate  or  nitrate  solution, 
in  the  escaping  steam  from  the  short  tube.  As  long  as  any  hydrogen 
sulphide  is  present  the  paper  is  blackened  or  browned.  The  solution 
must  be  cooled  in  a  current  of  carbon  dioxide  before  titration  with 
permanganate. 

In  dissolving  the  oxides  of  iron  and  aluminum  in  potassium  bisul- 
phate,  the  operation  should  be  conducted  at  a  low  temperature,  so  as 
not  to  drive  off  the  excess  acid  in  the  salt.  The  contents  of  the  crucible 
should  therefore  be  just  hot  enough  to  keep  them  fluid.  The  fusion 
with  bisulphate  is  tedious,  however,  and  until  recently  the  writer  de- 
termined ferric  oxide  in  cement  by  the  following  methods.  It  is  simpler 


THE    ANALYSIS    OF 


275 


than  the  above  schemes  and  has  the  advantage  of  allowing  a  sample  of 
one  or  two  grams  to  be  used  for  the  determinations : 

Weigh  i  gram  of  finely  ground  cement  into  a  beaker  and  add  15  cc. 
of  hydrochloric  acid.  Heat  for  ten  to  fifteen  minutes,  add  200  cc.  of 
water  and  heat  to  boiling.  Add  ammonia  in  slight  but  distinct  excess, 
boil  a  few  minutes,  allow  the  precipitate  to  settle,  filter,  using  the  filter- 
pump  if  one  is  at  hand,  and  wash  two  or  three  times  with  hot  water. 
Place  a  clean  flask  under  the  funnel  and  redissolve  the  precipitate  in  a 
mixture  of  15  cc.  dilute  sulphuric  acid  and  60  cc.  water,  made  up  in  the 
beaker  in  which  the  precipitation  was  effected.  Wash  the  filter  and  silica 
free  from  iron  with  cold  water,  pass  through  the  reductor,  described 
below,  and  titrate  the  solution  with  permanganate.  Multiply  the  num- 


Fig.  86.— Shimer's  reductor. 

ber  of  cubic  centimeters  of  standard  permanganate  required  by  the  ferric 
oxide  value  of  the  permanganate  and  then  by  100.  Divide  the  result 
by  the  weight  of  cement  taken;  the  quotient  will  be  the  per  cent,  of 
ferric  oxide,  Fe2O3,  in  the  cement. 

The  form  of  reductor  best  suited  to  cement  work  is  the  design  of 
Dr.  Porter  W.  Shimer,  of  Easton,  Pa.  His  description  of  the  apparatus1 
is  as  follows:  "The  reductor  tube  (Fig.  86)  is  a  plain  glass  tube,  three- 
eights  inch  internal  diameter,  drawn  out  and  cut  off  at  its  lower  end. 
It  is  filled  by  placing  a  few  small  pieces  of  broken  glass  in  the  drawn 

1  Jour.  Amer.  Chem.  Soc.,  XXI,  723. 


276  PORTLAND  CEMENT 

out  portion,  and  on  this  about  an  inch  of  well  cleaned  sand.  The  tube 
is  then  filled  with  amalgamated  zinc  of  as  nearly  uniform  twenty  mesh 
size  as  possible.  About  80  grams  are  required.  No  asbestos  or  glass 
wool  is  used.  The  sand  prevents  particles  of  zinc  from  falling  through 
and  it  does  not  become  clogged  by  use.  The  consumption  of  zinc  is 
very  small,  and  when  the  column  has  settled  about  an  inch  a  little  fresh 
zinc  can  easily  be  poured  in  from  above.  The  reductor  tube  is  united 
with  a  4-inch  funnel  by  means  of  rubber  tubing,  well  tightened  with 
wire.  Between  the  funnel  and  reductor  is  a  Hoffman  clamp.  The  lower 
end  of  the  tube  passes  through  a  soft  two  hole  stopper  so  far  as  to  reach 
half  way  to  the  bottom  of  a  heavy-walled  pint  gas  bottle.  The  gas 
bottle  is  connected  with  a  filter-pump  through  an  intermediate  safety 
bottle  and  valve.  The  funnel  is  clamped  to  a  retort  stand  in  such  a 
manner  as  to  allow  the  tube  and  gas  bottle  to  swing  easily  in  all  direc- 
tions. It  is  well  to  adjust  the  height  so  as  to  leave  the  gas  bottle 
raised  slightly  above  the  base.  The  passage  of  the  solution  through  the 
reductor  may  be  effected  either  by  use  of  the  pump  or  by  means  of  a 
vacuum  obtained  by  condensation  of  steam  devised  originally  in  Bun- 
sen's  laboratory.  In  using  the  latter  method  a  little  water  may  be  boiled 
in  the  gas  bottle  until  all  air  is  expelled,  and  then  quickly  unite  with  the 
reductor,  the  clamp  on  the  filter-pump  being  closed.  The  speed  of  fil- 
tration is  regulated  by  the  upper  clamp.  Instead  of  filling  the  gas 
bottle  with  steam  by  boiling  water  in  it,  it  is  better  to  have  a  con- 
venient tin  or  copper  can  containing  boiling  water  and  provided  with 
one  or  more  short  steam  outlet  tubes  on  top.  The  empty  gas  bottle  is 
inverted  over  one  of  these  steam  outlets  and  when  filled  with  live  steam, 
is  taken  off  and  united  as  quickly  as  possible  with  the  reductor.  This 
latter  method  has  the  advantage  of  starting  with  an  empty  gas  bottle 
which  is  desirable  on  the  score  of  accuracy." 

To  use  the  reductor  first  pass,  by  the  aid  of  suction,  about  50  cc. 
of  cold  dilute  sulphuric  acid  (i  part  acid  to  20  parts  of  water)  through 
the  reductor,  and  then  follow  with  200  cc.  of  cold  distilled  water.  The 
Hoffman  clamp  should  be  closed  before  all  the  water  has  run  out  of  the 
funnel  so  as  to  keep  the  tube  full  of  water.  Now  empty  the  flask, 
again  attach  to  the  tube,  pour  the  iron  solution  into  the  funnel  and 
open  the  clamp.  Just  before  the  funnel  becomes  empty,  run  water 
around  its  sides  and  rinse  the  beaker  well  with  water,  running  the 
washings  also  through  the  reductor,  using  about  100  to  150  cc.  of  water 
to  wash  the  funnel  and  beaker.  The  time  required  for  the  iron  solu- 
tion to  filter  through  the  zinc,  should  be  regulated  by  the  upper  clamp 
to  occupy  from  three  and  a  half  to  five  minutes. 

Instead  of  reducing  the  iron  solution  by  means  of  a  reductor,  the  gas 
bottle,  mentioned  on  page  272,  may  be  used.  Pour  the  solution  into 
the  bottle.  Add  I  gram  of  granulated  zinc,  stopper  and  allow  to  stand 


THE   ANALYSIS    OF    CEMENT  277 

until  the  evolution  of  hydrogen  slackens;  then  heat  to  boiling.  When 
the  zinc  is  completely  dissolved  (it  may  be  necessary  to  add  more  acid 
to  effect  this),  push  down  the  glass  tube,  cool,  and  after  adding  10  cc. 
of  dilute  sulphuric  acid  titrate  with  the  permanganate. 

The  reduction  may  be  accomplished  with  hydrogen  sulphide  also.  The 
idea  of  the  use  of  hydrogen  sulphide  is  to  do  away  with  the  error 
introduced  by  the  presence  of  a  small  percentage  of  titanium,  always 
found  in  cement.  Titanium  is  reduced  by  zinc,  and  then  oxidized  by 
permanganate,  causing  the  results  for  iron  to  be  high.  It  is  not  re- 
duced by  hydrogen  sulphide,  hence  the  use  of  the  latter.  If  the  tita- 
nium is  not  determined  and  deducted  from  the  alumina,  however,  the  lat- 
ter is  too  high,  by  just  so  much,  so  that  for  practical  purposes  we  might 
as  well  call  titanium  iron  and  use  zinc  as  a  reducing  agent,  as  call  it 
aluminium  and  use  hydrogen  sulphide. 

By  Titration  with  Potassium  Bichromate.     (Penny's  Method.) 
Standard  Potassium  Bichromate. 

Place  from  10  to  15  grams  of  C.  P.  potassium  bichromate  in  a 
sufficiently  large  platinum  crucible.  Heat  carefully,  avoiding  all 
contact  of  the  flame  with  the  contents  of  the  crucible,  until  the 
salt  just  fuses  to  a  dark  liquid.  Then  withdraw  at  once  from 
the  flame  and  let  the  crucible  cool.  Weigh  3.074  grams  of  the 
fused  bichromate,  which  in  cooling  will  have  crumbled  to  a  pow- 
der, dissolve  in  250  to  300  cc.  of  cold  water  and  pour  into  a 
liter  graduated  flask.  Rinse  out  the  beaker  several  times  into 
the  flask  and  dilute  the  solution  to  the  liter  mark.  Mix  well. 
One  cc.  of  this  solution  should  be  equivalent  to  0.005  gram  of 
ferric  oxide,  Fe2O3. 

To  test  or  standardize  the  solution,  weigh  into  a  small  beaker 
0.4900  gram  of  pure  ferrous  ammonium  sulphate  (equivalent  to 
o.i  gram  of  ferric  oxide).  Dissolve  in  50  cc.  of  water  and,  when 
all  the  salt  is  in  solution,  add  5  cc.  of  dilute  hydrochloric  acid. 
Run  the  bichromate  solution  from  a  burette  into  the  liquid  in  the 
beaker  until  a  drop  of  the  iron  solution  placed  upon  a  white 
porcelain  plate  and  mixed  by  stirring  with  a  drop  of  freshly 
made  I  per  cent,  solution  of  potassium  ferricyanide  no  longer 
assumes  a  blue  color,  but  instead  gives  a  yellow.  This  should 
require  20  cc.  of  the  bichromate  solution.  If  more  or  less,  re- 
peat the  test,  and  if  the  first  and  second  results  agree,  divide  o.i, 


278  PORTLAND  CEMENT 

the  ferric  oxide  equivalent  of  the  weight  of  the  ferrous  am- 
monium sulphate  use,  by  the  number  of  cubic  centimeters  of 
bichromate  required.  The  result  will  give  the  ferric  oxide  equiv- 
alent, or  value,  in  grams  for  each  cubic  centimeter  of  the  standard 
potassium  bichromate. 

Some  operators  prefer  to  standardize  their  bichromate  against 
iron  wire.  In  this  case  clean  o.i  gram  of  fine  iron  wire  by  rub- 
bing between  fine  emery  paper  and  then  between  filter-paper. 
Coil  around  a  lead  pencil  and  weigh.  Drop  the  coil  in  a  small 
beaker,  add  20  cc.  of  dilute  hydrochloric  acid  and  heat  until  all 
the  wire  dissolves.  Wash  down  the  sides  of  the  beaker  with  a 
wash-bottle,  bring  the  contents  to  a  boil  and  drop  in.  the  stan- 
nous  chloride  solution,  described  below,  slowly  until  the  last  drop 
turns  the  solution  colorless.  Remove  from  the  source  of  heat  and 
cool  the  liquid  rapidly  by  setting  the  dish  in  a  vessel  of  cold  water. 
When  nearly  cold  add  at  once  15  cc.  of  saturated  mercuric  chlor- 
ide solution,  and  stir  well.  Allow  to  stand  a  few  minutes  and 
titrate  with  the  bichromate  as  described  above.  Multiply  the 
weight  of  the  iron  wire  by  0.003  and  deduct  this  from  the  origi- 
nal weight,  for  the  impurities  in  the  wire.  The  corrected  weight 
divided  by  0.7  and  then  by  the  number  of  cubic  centimeters  of  bi- 
chromate required,  gives  the  ferric  oxide  equivalent  in  grams  to 
each  cubic  centimeter  of  the  standard  bichromate.  This  value 
should  be  checked  unless  within  limits  of  allowable  error  to 
0.005  gram. 

Stannous  Chloride  Solution. 

Dissolve  loo  grams  of  stannous  chloride  in  a  mixture  of  300 
cc.  of  water  and  100  cc.  of  hydrochloric  acid.  Add  scraps  of 
metallic  tin  and  boil  until  the  solution  is  clear  and  colorless. 
Keep  this  solution  in  a  closely  stoppered  bottle  (best  a  dropping 
bottle)  containing  metallic  tin.  This  solution  should  be  kept  from 
the  air. 

Mercuric  Chloride  Solution. 

Make  a  saturated  solution  of  mercuric  chloride  by  putting  an 
excess  of  the  salt  in  a  bottle  and  filling  up  with  water  and  shak- 
ing as  the  solution  gets  low. 


THE    ANALYSIS    OF    CEMENT  2/9 

The  Determination. 

Weigh  i  gram  of  finely  ground  cement  into  a  small  beaker  and 
add  15  cc.  of  dilute  hydrochloric  acid,  heat  from  ten  to  fifteen 
minutes  and  add  a  little  water.  Heat  to  boiling  and  filter  through 
a  small  filter,  washing  the  residue  well  with  water  and  catching 
the  filtrate  and  washings  in  a  porcelain  dish.  Add  to  the  solu- 
tion 5  cc.  of  dilute  hydrochloric  acid  and  bring  to  a  boil.  Add 
carefully,  drop  by  drop,  the  stannous  chloride  solution  until  the 
last  drop  makes  the  solution  colorless.  Remove  from  the  burner 
and  cool  the  liquid  by  setting  in  a  vessel  of  cold  water.  When 
nearly  cold  add  15  cc.  of  the  mercuric  chloride  solution  and  stir 
the  liquid  in  the  dish  with  a  glass  rod.  Allow  the  mixture  to 
stand  for  a  few  minutes,  during  which  time  a  slight  white  pre- 
cipitate should  form.  Run  in  the  standard  bichromate  solution 
carefully  from  a  burette  until  a  drop  of  the  iron  solution  tested 
with  a  drop  of  I  per  cent,  solution  of  potassium  ferricyanide  no 
longer  shows  a  blue,  but  instead  a  yellow  color.  Multiply  the 
number  of  cubic  centimeters  of  bichromate  used  by  the  ferric 
oxide  equivalent  per  cubic  centimeter  of  the  bichromate  and 
d'vide  the  product  by  the  weight  of  the  sample.  The  result  mul- 
tiplied by  zoo  gives  the  per  cent,  of  the  ferric  oxide,  Fe2O3,  in 
the  cement. 

NOTES. 

Treatment  with  hydrochloric  acid  is  sufficient  to  dissolve  all  except 
a  mere  trace  of  iron  in  Portland  cement. 

A  strongly  acid  solution  of  ferric  chloride,  if  boiling  hot,  is  instantly 
reduced  to  ferrous  chloride  by  a  solution  of  stannous  chloride  accord- 
ing to  the  following  reaction : 

Fe2Cl9  +   SnCU  =  SnCU  +   2FeCl2. 

The  operator  can  tell  when  complete  reduction  has  taken  place  by  the 
disappearance  of  the  yellow  color  of  the  solution.  The  excess  of  stan- 
nous chloride  is  removed  by  addition  of  mercuric  chloride  when  the 
following  takes  place: 

SnCl2  +  2HgCl3  =  SnCl*  +  Hg2Cl* 

The  precipitate,  Hg2Cl2  should  be  white ;  if  colored  gray  too  much  stan- 
nous chloride  was  used  in  reduction  and  mercury  has  been  formed.  As 
mercury  reacts  with  the  bichromate,  when  the  precipitate  formed  on  add- 
ing mercuric  chloride  is  not  perfectly  white,  but  is  colored  gray,  the 


280  PORTLAND  CEMENT 

determination  should  be  repeated  using  more  care  to  avoid  a  large  excess 
of  the  tin  solution.  If  no  precipitate  is  formed  on  addition  of  mer- 
curic chloride  the  stannous  chloride  has  not  been  added  in  excess,  and 
all  the  iron  will  not  have  been  reduced  to  the  ferrous  state. 

Ferrous  salts  are  oxidized  to  ferric  compounds  by  bichromate  when 
in  a  solution  containing  a  considerable  excess  of  hydrochloric  or  sul- 
phuric acid.  The  reaction  is. 

6FeCl2  +  KaCR207  +  I4HC1  =  3Fe2Cl8  +  Cr2Cl6  +  2KC1  +  ;H2O. 

The  ferrous  ammonium  sulphate  has  the  formula  Fe(NHO  2(80)4)2. 
6H2O.  It,  therefore  contains  one-seventh  its  weight  of  iron  and  is 
equivalent  to  0.20408  of  its  weight  of  ferric  oxide,  Fe2Os.  Fe2Os. 

To  make  a  I  per  cent,  solution  o<f  potassium  ferricyanide  dissolve 
i  gram  of  the  salt  in  100  cc.  of  water.  Ferric  compounds  give  a  yellow 
color  to  this  solution,  while  ferrous  compounds  impart  an  intense  blue 
color.  This  solution  must  always  be  made  up  fresh  as  it  is  reduced  by 
exposure  to  light. 

The  writer  has  experimented  considerably  with  the  above  method  dur- 
ing the  past  year,  and  he  has  found  it  thoroughly  reliable.  The  pres- 
ence of  titanium  does  not  affect  its  accuracy  and  a  determination  can 
easily  be  made  in  from  15  to  20  minutes. 

DETERMINATION  OF  SULPHURIC  ACID. 
Gravimetric  Method. 

Weigh  one  gram  of  the  sample  into  a  small  dry  beaker  and 
stir  it  up  with  10  cc.  of  cold  water  until  all  lumps  are  broken  up 
and  the  lighter  particles  are  in  suspension.  Add  15  cc.  of  dilute 
(i-i)  hydrochloric  acid  and  heat  until  solution  is  complete.  Fil- 
ter through  a  small  paper  and  wash  the  residue  thoroughly.  Di- 
lute the  filtrate  to  250  cc.,  heat  to  boiling,  and  add  10  cc.  of  boil- 
ing 10  per  cent,  barium  chloride  solution.  Stir  well  and  allow  to 
stand  over  night.  Filter,1  ignite,  and  weigh  as  BaSO4,  which 
multiplied  by  0.34300  gives  SO3,  or  by  0.58327,  gives  calcium 
sulphate,  CaSO4.  In  this  latter  case  multiply  the  percentage  of 
calcium  sulphate  by  0.41195  and  deduct  from  the  percentage  of 
lime  for  the  true  percentage  of  calcium  oxide,  CaO. 

Photometric  Method. 

Jackson2  has  devised  a  rapid  photometric  method  for  deter- 

1  See  note,  p.  206. 

2  Chemical  Engineer,  I.,  6,  361. 


THE    ANALYSIS    OF 


28l 


mining  sulphuric  acid  which  is  very  convenient  for  checking  this 
constituent  in  a  large  number  of  samples. 

The   apparatus1   used  in  this   method  is   shown  in   Fig.   87. 


Fig.  87. — Jackson's  apparatus  for  the  photometric  determination  of  sulphates. 

Above  is  a  glass  tube  closed  at  the  bottom  and  graduated  in  milli- 
meters depth.     A  convenient  form  of  tube  is  a  Nessler  jar  2.5 

1  Made  by  Baker  &  Fox,  83  Schermerhom  St.,  Brooklyn,  N.  Y. 


282  PORTLAND  CEMENT 

cm.  in  diameter  and  17  cm.  to  the  100  cc.  mark.  The  brass  holder 
for  this  tube  is  open  at  the  bottom  so  that  the  glass  tube  rests 
on  a  narrow  ring  at  this  point.  The  candle  below  is  so  adjusted 
by  means  of  a  spring  that  the  top  edge  is  always  just  three  inches 
below  the  bottom  of  the  glass  tube.  The  illustration  shows  the 
candle  with  the  regulator  cap  removed  so  as  to  better  represent 
the  process.  The  English  Standard  Candle  is  preferred,  but  a 
common  candle  of  the  same  size  may  be  used.  This  candle  must 
always  be  properly  trimmed  and  the  determination  must  be  made 
rapidly  so  as  not  to  heat  the  liquid  to  any  extent.  The  most  ac- 
curate work  is  obtained  in  the  dark  room,  and  the  candle  should 
be  so  placed  as  not  to  be  subjected  to  a  draft  of  air.  Care  should 
be  taken  to  keep  the  bottom  of  the  tube  clean  both  inside  and  out 
so  as  not  to  cut  out  any  of  the  light. 

To  determine  the  sulphate  in  a  cement  weigh  out  one  gram, 
correct  to  centigrams,  and  rub  up  thoroughly  with  a  glass  rod  in 
a  small  porcelain  dish,  or  casserole,  with  two  cubic  centimeters  of 
strong  hydrochloric  acid.  Add  about  ten  cubic  centimeters  of 
water  and  heat  to  boiling.  Filter  and  wash  with  a  small  amount 
of  hot  water  into  a  100  cc.  graduated  Nessler  jar,  and  fill  with 
cold  water  nearly  to  the  100  cc.  mark.  If  necessary  suction  may 
be  employed  in  filtering,  but  usually  a  folded  rib  filter  will  do. 
Now  add  two  grams  of  solid  barium  chloride  crystals  and  make 
up  to  the  100  cc.  mark  with  cold  distilled  water.  Pour  back  and 
forth  from  the  tube  to  a  beaker  until  all  of  the  barium  chloride  is 
dissolved.  The  solution  is  now  ready  for  examination. 

The  candle  is  trimmed  and  lighted ;  the  solution  is  poured  back 
and  forth  to  get  a  thorough  mixture  of  the  precipitate  of  barium 
sulphate;  and  the  glass  tube  is  placed  in  position  in  the  holder. 
The  liquid  containing  the  precipitate  is  now  poured  into  a  grad- 
uated tube  until  the  sight  of  the  image  of  the  flame  of  the  candle 
is  just  visible.  Then  pour  in  a  few  drops  at  a  time  until  it  just 
disappears  from  view.  The  height  to  which  this  solution  stands 
in  the  tube  (reading  the  bottom  of  the  meniscus)  is  then  taken 
and  from  this  reading  the  percentage  of  sulphates  present  in  the 
cement  may  be  read  directly  from  the  following  table: 


THE    ANALYSIS    OF    CEMENT 


TABLE  XIX. — FOR  THE  DETERMINATION  OF  SULPHATE  IN  CEMENT. 


Depth 

Per  cent. 

Depth 

Per  cent. 

Depth 

Per  cent. 

Depth 

Per  cent. 

cm. 

SO3. 

cm. 

S03. 

cm. 

S03- 

cm. 

S03. 

.0 

5-2 

4.0 

•  4 

7.0 

0.8 

IO.O 

0.6 

.1 

4.8 

4.1 

•4 

7-1 

0.8 

10.2 

0.6 

.2 

4.4 

4-2 

•3 

7-2 

0.8 

10.4 

0.6 

•3 

4.1 

4-3 

•3 

7-3 

0.8 

10.6 

0-5 

•4 

3-8 

4.4 

•3 

7-4 

0.8 

10.8 

0.5 

•5 

3-6 

4-5 

•3 

7-5 

0.8 

II.  O 

°-5 

•6 

3-4 

4.6 

.2 

7-6 

0.8 

II.  2 

o.5 

•7 

3-2 

4-7 

.2 

7-7 

0.7 

II.4 

0-5 

.8 

3-o 

4-8 

.2 

7.8 

0.7 

II.  6 

0-5 

•9 

2.9 

4-9 

.2 

7-9 

0.7 

n.8 

°-5 

2.0 

2-7 

5-0 

.1 

8.0 

0.7 

I2.O 

0.5 

2.1 

2.6 

5-1 

.1 

8.1 

0.7 

12.2 

0-5 

2.2 

2-5 

5.2 

.1 

8.2 

0.7 

12.4 

0-5 

2-3 

2.4 

5-3 

.1 

8.3 

0.7 

12.6 

0.5 

2.4 

2-3 

5-4 

.0 

8.4 

0.7 

12.8 

0.4 

2-5 

2.2 

5-5 

.O 

8-5 

0.7 

13.0 

0.4 

2.6 

2.1 

5-6 

.O 

8.6 

0.7 

13-5 

0.4 

2-7 

2.1 

5-7 

.O 

8.7 

0.7 

14.O 

0.4 

2.8 

2.O 

5.8 

.O 

8.8 

0.6 

14-5 

0.4 

2.9 

•9 

5-9 

.O 

8.9 

0.6 

15.0 

0.4 

3.0 

6.0 

0.9 

9.0 

0.6 

15-5 

0.4 

3.1 

.8 

6.1 

0.9 

9-i 

0.6 

16.0 

0.4 

3-2 

•  7 

6.2 

0.9 

9.2 

0.6 

16.5 

0.4 

3-3 

•  7 

6-3 

0-9 

9-3 

0.6 

17.0 

0-3 

3-4 

.6 

6.4 

0.9 

94 

0.6 

17.5 

o-3 

3-5 

.6 

6.5 

0.9 

9-5 

0.6 

18.0 

0-3 

3-6 

1.6 

6.6 

0.9 

9.6 

0.6 

18.5 

0.3 

3-7 

1-5 

6-7 

0.8 

9-7 

0.6 

19.0 

0-3 

3-8 

1-5 

6.8 

0.8 

9-8 

0.6 

195 

0-3 

3-9 

1.4 

6-9 

0.8 

9-9 

0.6 

20.0 

o-3 

DETERMINATION  OF  TOTAL  SULPHUR. 
By  Solution  in  HC1  and  Br. 

Weigh  one  gram  of  the  sample  into  a  dry  beaker  and  stir  it  up 
with  30  cc.  of  bromine  water  until  all  lumps  are  broken  up  and 
all  except  the  heavier  particles  are  in  suspension.  Add  15  cc.  of 
dilute  hydrochloric  acid  (i-i)  and  heat  until  solution  is  complete. 
Filter  off  the  residue  through  a  small  filter  and  wash  thoroughly 
with  hot  water.  Dilute  to  250  cc.  and  boil  until  all  bromine  is 
expelled.  Now  to  the  boiling  solution  add  10  cc.  of  10  per  cent, 
barium  chloride  solution,  also  boiling,  and  proceed  as  in  the  de- 
termination of  sulphates. 


284  PORTLAND  CEMENT 

By  Fusion  With  Na2C03  and  KN03. 

Place  i  gram  of  cement,  finely  ground  and  dried,  in  a  large 
platinum  crucible  and  thoroughly  mix  it  by  stirring  with  6  grams 
of  sodium  carbonate  and  a  little  sodium  or  potassium  nitrate. 

Fuse  the  mixture,  being  careful  to  avoid  contamination  from 
sulphur  in  the  gases  from  source  of  heat.  This  may  be  done  by 
fitting  the  crucible  in  a  hole  in  an  asbestos  board.  THe  heating  of 
the  crucible  should  be  gradually  done  first  over  a  Bunsen  burner 
for  a  while  and  then  over  a  blast  lamp,  until  the  contents  of  the 
crucible  are  in  quiet  fusion.  Run  the  fused  mass  well  up  on  the 
sides  of  the  crucible  and  chill  by  dipping  the  bottom  of  the  cru- 
cible in  a  vessel  of  cold  water.  If  loose,  remove  the  mass  from 
the  crucible  to  a  beaker  and  cover  with  hot  water.  If  not  loose, 
fill  the  crucible  with  hot  water  and  digest  until  the  mass  breaks 
up;  then  remove  to  the  beaker.  Cover  the  latter  with  a  watch- 
glass  and  acidify  with  hydrochloric  acid.  When  effervescence 
ceases  remove  the  watch-glass,  rinse  into  the  dish  and  filter.  Di- 
lute the  filtrate  to  250  cc.  and  heat  to  boiling.  Add  10  cc.  of  10 
per  cent,  barium  chloride  solution,  also  heated  to  boiling.  Stir 
and  heat  for  a  few  minutes  and  proceed  as  in  the  determination 
of  sulphates. 

DETERMINATION  OF  SULPHUR   PRESENT  AS 
CALCIUM  SULPHIDE. 

Weigh  5  grams  of  cement  into  a  porcelain  dish,  and  triturate 
with  water  until  it  shows  no  further  tendency  to  set.  Then  wash 
out  into  the  flask  (Fig.  88)  and  cork  tightly.  Two-thirds  fill  the 
ten-inch  test-tube  with  a  solution  of  lead  oxide  in  caustic  potash 
made  by  adding  lead  nitrate  solution  to  potassium  hydroxide  so- 
lution (sp.  gr.  1.27)  until  a  permanent  precipitate  forms,  and  then 
filtering  off  the  solution  through  asbestos  after  allowing  the  pre- 
cipitate to  settle.  Run  into  the  flask  by  means  of  the  funnel  50 
cc.  of  dilute  hydrochloric  acid  and  apply  heat  gently.  Finally 
bring  the  acid  to  a  boil  and  disconnect  the  delivery  tube  from  the 
flask  at  the  rubber  joint.  Collect  the  precipitate  on  a  small  filter, 
wash  it  once  with  water  and  then  while  still  moist  throw  the  pre- 
cipitate and  filter  back  into  the  test-tube,  in  which  has  been  placed 


THE)    ANALYSIS    OF    CEMENT 

some  powdered  potassium  chlorate.  Pour  upon  the  filter  and  pre- 
cipitate 10  cc.  of  concentrated  hydrochloric  acid.  Allow  to  stand 
in  a  cool  place  until  the  fumes  have  passed  off,  then  add  25  cc. 
of  hot  water,  filter  off  the  pulp,  etc.,  and  wash  with  hot  water. 
Heat  the  filtrate  to  boiling  and  add  ammonia  until  the  solution  is 
slightly  alkaline.  Then  acidulate  with  a  few  drops  of  hydrochlo- 
ric acid,  add  10  cc.  of  a  10  per  cent,  solution  of  barium  chloride, 
also  brought  to  a  boil,  boil  for  a  few  minutes  and  stand  in  a  cool 
place  over  night.  Filter,  wash,  ignite,  and  weigh  as  barium  sul- 


Fig.  88.— Apparatus  for  determining  sulphides. 

phate.     Multiply  this   weight  by  0.30895   for  calcium   sulphide, 
CaS,  or  by  0.13738  for  sulphur,  S. 

NOTES. 

Instead  of  alkaline  lead  nitrate  solution  a  solution  of  cadmium  chlo- 
ride made  slightly  alkaline  with  ammonia  may  be  used  to*  absorb  the 
evolved  hydrogen  sulphide,  in  which  case  the  cadmium  sulphide  pre- 
cipitated, may  be  collected  upon  a  previously  weighed  filter-paper,  dried, 
weighed  and  the  sulphur  calculated  from  this  weight.  For  this  method 
use  10  grams  of  cement  for  the  sample  and  fill  the  test-tube  two-thirds 
full  of  a  solution  of  cadmium  chloride,  made  by  dissolving  3  grams  of 
cadmium  chloride  in  75  cc.  of  water,  adding  ammonia  until  the  pre- 
cipitate at  first  formed  redissolves  and  then  diluting  to  500  cc.  Proceed 
as  usual.  Collect  the  precipitate  of  cadmium  sulphide  upon  a  small 
counterpoised  filter,  or  better  in  a  Gooch  crucible  and  felt,  wash  with 


286  PORTLAND  CEMENT 

water  to  which  a  little  ammonia  has  been  added,  dry  at  100°  C.,  and 
weigh  as  cadmium  sulphide,  CdS.  The  weight  of  cadmium  sulphide 
multiplied  by  0.5000  gives  the  equivalent  amount  of  calcium  sulphide. 
Calculate  the  percentage  and  report  as  such  or  merely  report  as  sulphur. 
If  the  former,  calculate  the  total  sulphur,  as  found  by  either  of  the 
methods  on  pages  59-60  to  calcium  sulphate,  by  multiplying  the  weight 
of  the  barium  sulphate  by  0.58327.  Now  multiply  the  percentage  of 
calcium  sulphate  so  found  by  0.41195  and  deduct  the  product  from  the 
percentage  of  lime  (as  found  by  precipitation  as  oxalate  in  the  general 
scheme).  The  difference  should  be  reported  as  calcium  oxide,  or  lime, 
CaO.  Multiply  the  percentage  of  calcium  sulphide  by  1.8872  for  its 
equivalent  in  calcium  sulphate  and  deduct  from  the  percentage  of  total 
sulphur  calculated  as  calcium  sulphate.  Report  the  difference  as  cal- 
cium sulphate. 

Calcium    sulphide   may   also   be    determined    indirectly   by   determining 


Fig.  89.— Shimer's  filter  tube. 

first  the  sulphur  present  as  sulphate  and  then  the  total  sulphur.  The 
difference  will  represent  the  sulphur  present  as  sulphide.  This  may 
be  reported  either  as  CaS  or  as  S.  By  this  method,  however,  errors  are 
made  to  appear  as  CaS. 

Barium  sulphate  is  a  troublesome  precipitate  to  filter  as  it  is  likely 
to  run  through  the  paper.  For  this  reason  it  is  well  to  use  a  double 
paper.  Some  operators  use  a  Gooch1  crucible,  but  a  device  suggested 
by  Dr.  Porter  W.  Shimer,  of  Easton,  Pa.,  is  still  handier.  It  is  shown 
in  its  simplest  form  in  Fig.  89.2  It  consists  of  a  glass  tube  cut  off 
square  at  both  ends,  two  inches  long  and  one  inch  in  internal  diameter. 
The  edges  should  be  left  sharp  and  not  rounded  in  the  flame.  In  the 

1  See  page  184. 

2  Jour.  Amer.  Chem.  Soc.,  XXVII.,  287.     Chemical  Engineer,  II.,  39. 


ANALYSIS    OF    CEMENT  287 

bottom  of  the  tube  is  a  rubber  stopper  fitted  with  a  glass  tube  for 
attachment  to  the  suction  flask.  On  the  stopper  when  inserted  into  the 
tube  is  a  disk  of  piano  felt  3/16  inch  thick,  fitting  closely  into  the  tube. 
The  filter  tube  is  now  ready  for  the  filter.  Take  unwashed  Swedish 
filter-paper,  in  any  convenient  amount,  crush  it  into  a  ball  in  the  hand 
and  place  it  in  a  large  cerecene  hydrofluoric  acid  bottle  from  which  the 
upper  part  has  been  cut.  Add  hydrochloric  acid  (sp.  gr.  1.12  to  1.18) 
and  a  little  hydrofluoric  acid  and  stir  vigorously  with  a  paraffin-coated 
wooden  stirrer  until  the  paper  has  become  a  mass  of  fine  soft  pulp.  Let 
it  stand  a  few  minutes  and  then  add  distilled  water.  In  preparing  a 
filter,  pour  some  of  this  pulp  in  the  beaker,  dilute  further  with  distilled 
water  and  pour  enough  on  the  felt,  under  suction,  to  make  a  filter 
of  about  %  inch.  Compact  this  well  by  hard  stamping  with  a  stamper 
made  from  a  solid  rubber  stopper,  the  larger  end  of  which  is  only  a  little 
smaller  than  the  inner  diameter  of  the  tube.  A  hole  is  made  in  the 
small  end  of  the  stopper,  but  not  deep  enough  to  pass  quite  through 
and  a  short  glass  rod  inserted  in  this  for  a  handle.  Wash  the  filter 
two  or  three  times  with  water  and  then  filter  off  and  wash  the  barium 
sulphate,  using  suction.  This  may  be  done  rapidly  without  fear  of  a 
trace  of  the  precipitate  getting  into  the  filtrate. 

xWhen  filtration  and  washing  are  complete,  turn  off  the  suction  and 
remove  the  filter  tube  from  the  stopper.  Take  the  stamper  and  push 
the  felt  up  until  the  filter  projects  beyond  the  tube,  when  the  filter  may 
be  detached  from  the  felt  by  a  pair  of  forceps,  or,  if  preferred,  the 
upper  end  of  the  tube  may  be  inserted  into  the  weighed  crucible  and  the 
felt  and  filter  may  be  pushed  at  once  into  it,  when  the  felt  can  be  readily 
removed  and  the  precipitate  and  filter  ignited.  Any  precipitate  adhering 
to  the  sides  of  the  tube  is  taken  along  by  the  outgoing  filter,  for  this 
reason  the  tube  should  be  of  uniform  diameter,  etc.  The  ash  of  these 
filters  is  less  than  that  of  an  ordinary  filter  and  the  apparatus  gives  ex- 
cellent results.  It  may,  of  course,  be  used  for  making  other  filtrations, 
but  is  particularly  well  adapted  for  use  with  barium  sulphate. 

It  now  seems  to  be  pretty  well  established  that  it  is  not  necessary  to 
evaporate  to  dryness  and  separate  silica,  before  precipitating  sulphur 
with  barium  chloride,  provided  the  solution  is  sufficiently  dilute  to  guard 
against  separation  of  gelatinous  silica. 

LOSS  ON  IGNITION. 

Weigh  0.5  gram  of  cement  into  a  weighed  platinum  crucible, 
cover  with  a  lid,  and  heat  for  five  minutes  over  a  Bunsen  burner, 
starting  with  a  low  flame  and  gradually  raising  it  to  its  full 
height.  Then  heat  for  fifteen  minutes  over  a  blast  lamp.  Cool 
and  weigh.  The  loss  of  weight  represents  the  loss  on  ignition. 


288  PORTLAND  CEMENT 

This  loss  consists  mainly  of  combined  water  and  carbon  dioxide 
driven  off  by  the  high  temperature.  Some  chemists  report,  there- 
fore, as  "carbon  dioxide  and  water,"  or  having  found  the  carbon 
dioxide  subtract  the  percentage  from  that  of  the  "loss  on  igni- 
tion" and  call  the  remainder  "water  of  combination"  or  com- 
bined water.  As  both  sulphuric  acid  and  alkalies  are  driven  off, 
to  some  extent,  at  the  temperature  of  the  blast  lamp,  this  is  not 
strictly  correct  and  it  is  best  to  merely  report  as  "loss  on  igni- 
tion." This  loss  of  alkalies  is  shown  by  the  fact  that  if  the  cruci- 
ble lid  is  rinsed  off  with  distilled  water,  after  the  crucible  has 
been  ignited  and  weighed,  and  is  then  ignited  for  a  moment  to 
dry  it  and  placed  back  on  the  crucible,  the  weight  of  the  whole 
will  be  from  0.5  milligram  to  1.5  milligram  lighter,  showing  the 
condensation  of  the  alkalies  on  the  lid. 

In  conducting  the  ignition  it  is  best  to  place  the  crucible  with  its 
bottom  projecting  through  a  round  hole  in  a  piece  of  platinum 
foil,  which  in  turn  rests  upon  a  piece  of  asbestos  board  with  a 
slightly  larger  hole  cut  in  it.  The  flame  should  be  played  at  an 
angle  upon  the  bottom  of  the  crucible  so  that  the  products  of 
combustion  are  swept  away  from  it.  , 

DETERMINATION  OF  CARBON  DIOXIDE  AND 
COMBINED  WATER. 

Apparatus. 

For  carrying  out  the  determination  of  carbon  dioxide  and  com- 
bined water  at  the  same  time,  the  apparatus  designed  by  Dr.  Por- 
ter W.  Shinier,  of  Easton,  Pa.,  for  carbon  combustions  is  best 
suited. 

The  apparatus  as  used  for  carbon  dioxide  and  combined  water 
determinations  is  illustrated  in  Fig.  90.  It  consists  of  the  follow- 
ing parts : 

1.  The  aspirator  bottles,  a'  and  a",  the  upper  a',  filled  with  dis- 
tilled water  and  the  tube  leading  to  the  lower  bottle  extending  to 
the  bottom  of  the  latter. 

2.  A  potash  bulb,  b,  containing  a  solution  of  caustic  potash  of 
1.27  sp.   gr.     The  form  of  bulb  shown  in  the  cut  is  Liebig's. 
Mohr's  or  any  other  form  will  do  as  well,  but  the  Liebig  bulb  is 


THE    ANALYSIS    OF    CEMENT 


289 


the  cheapest  and  answers  as  well  here  as  the  more  expensive 
forms. 

3.  A  U-tube,  c,  filled  with  dried  granular  calcium  chloride.     A 
straight  calcium  chloride  tube  may  be  used  in  place  of  the  U-tube. 
It  takes  up  more  room,  however. 

4.  A  platinum  crucible,  d,  provided  with  a  water- jacketed  stop- 
per and  reservoir,  e,  for  supplying  water  to  this  latter.     Fig.  91 
shows  the  crucible  stopper,  etc.,  in  detail.    The  water-cooled  stop- 
per is  made  of  German  silver  and  is  ground  into  the  crucible. 


Fig.  90.— Apparatus  for  determining  carbon  dioxide  and  water  with  Shimer's  crucible. 

This  joint  may  easily  be  kept  tight  by  an  occasional  grinding  in, 
using  for  this  purpose  a  little  glass  finely  ground  with  oil.  The 
crucible  is  of  60  cc.  capacity,  deep  in  form  and  weighs  about  50 
grams.  The  crucible  is  accurately  fitted  with  a  knurled  ring 
around  the  upper  part,  this  ring  is  easily  removed.  The  cruci- 
ble rests  with  its  bottom  through  a  circular  opening  in  a  piece  of 
3/16  inch  asbestos  board  which  in  turn  rests  upon  a  tripod. 

5.  A  small  U-tube,  ff  filled  with  dried  granular  calcium  chloride. 
The  best  form  is  that  shown,  provided  with  arms  and  glass  stop- 
cocks. 

6.  A  potash  bulb,  g,  with  calcium  chloride  tube  attached.     The 

19 


290 


PORTLAND  CEMENT 


bulb  should  be  filled  with  caustic  potash  of  1.27  specific  gravity, 
and  the  tube  with  dried  granular  calcium  chloride. 

7.  A  guard  tube,  h,  filled  with  dried  granular  calcium  chloride. 

Testing  the  Apparatus. 

Fill  the  reservoir,  e,  with  boiling  water.  Half  fill  the  crucible 
with  freshly  ignited  asbestos,  and  close  it  with  the  water-cooled 
stopper.  See  that  the  apparatus  is  perfectly  tight  by  running  the 


Fig.  91. — Shimer's  water-jacketed  crucible. 

aspirator  and  pinching  the  tube  together  just  after  the  potash 
bulb. 

Open  the  clamp  and  allow  water  to  run  out  of  the  stopper. 
Place  a  Bunsen  burner  under  the  crucible.  Open  the  clamp  be- 
tween the  lower  aspirator  bottle  and  the  potash  bulb,  b,  and  aspi- 
rate a  current  of  air  through  the  apparatus  slowly  for  about 
twenty  minutes.  Detach  the  potash  bulb,  g,  and  the  calcium 
chloride  tube  /,  and  weigh.  Again  connect  the  bulb  and  tube  in 
'the  train  and  aspirate  air  slowly  through  the  apparatus  for 
another  twenty  minutes.  Detach  the  bulb,  g,  and  tube,  /,  and 
again  weigh  them.  This  weight  should  agree  to  within  0.0005 
of  the  former  weight  for  the  potash  bulb,  and  0.0003  for  the  cal- 
cium chloride  tube.  If  not,  after  making  sure  there  is  no  leakage 


THE    ANALYSIS    OF    CEMENT  29! 

in  the  apparatus,  repeat  the  test.  When  the  weights  agree 
within  the  limits  given,  take  the  last  pair  as  the  weights  of  the 
bulb  and  tube,  and  proceed  with  the  determination. 

The  Determination. 

Weigh  into  the  crucible  from  I  to  3  grams  of  cement,  cover 
with  ignited  asbestos  and  stopper  tightly.  Test  the  apparatus  and 
be  sure  there  is  no  leakage.  Place  the  Bunsen  burner  under  the 
crucible  after  starting  the  hot  water  to  flowing  through  the  stop- 
per. Cause  a  slow  current  of  air  from-  the  aspirator  bottle  to  flow 
through  the  apparatus.  After  ten  minutes  replace  the  Bunsen 
burner  by  a  blast-lamp  and  continue  the  ignition  for  twenty  min- 
utes. Remove  the  lamp  and  aspirate  air  through  the  apparatus 
for  ten  minutes  longer.  Detach  the  potash  bulb,  gt  and  the  cal- 
cium chloride  tube,  /,  and  weigh.  The  increase  in  weight  of  the 
former  represents  the  carbon  dioxide,  CO,,  and  of  the  latter  water, 


NOTES. 

In  this  method  the  combined  water  and  the  carbon  dioxide  are 
driven  out  of  the  cement  by  ignition  ;  the  former  is  absorbed  in  a 
weighed  calcium  chloride  tube  and  the  latter  in  a  weighed  potash  bulb. 
The  increase  in  weight  of  the  tube  and  bulb  respectively  represent  the 
weight  of  combined  water  and  carbon  dioxide  in  the  cement  sample. 
The  air  entering  the  apparatus  for  the  purpose  of  aspiration  is  purified 
of  any  water  and  carbon  dioxide  it  is  sure  to  contain  by  passing  through 
the  caustic  potash  and  then  over  calcium  chloride. 

To  make  the  upper  aspirator  bottle,  bore  a  hole  near  the  bottom  of  a 
five  pint  bottle  with  a  file  dipped  in  turpentine  and  then  slip  into  this 
hole  a  bit  of  glass  tube  covered  with  an  inch  or  so  of  soft,  thick-walled 
rubber  tubing. 

To  fill  the  potash  bulbs  attach  a  short  piece  of  rubber  tubing  to  one 
end  and  dipping  the  other  end  in  the  caustic  potash  solution  contained 
in  a  shallow  dish  apply  suction  to  the  rubber  tubing  with  the  mouth. 
When  the  bulbs  are  filled  to  the  proper  height  (See  Fig.  90)  wipe  the 
end  dry  inside  and  outside  with  pieces  of  filter-paper. 

Instead  of  the  bulb,  b,  the  air  may  be  purified  of  any  carbon  dioxide 
it  contains  by  causing  it  to  bubble  through  caustic  potash  solution  con- 
tained in  two  4  ounce  wide  mouthed  bottles. 

Calcium  chloride  sometimes,  though  not  often,  contains  calcium  oxide, 
which  would  absorb  carbon  dioxide.  To  saturate  this,  connect  the  ap- 


292 


PORTLAND  CEMENT 


paratus,  leaving  out  the  potash  bulb,  /,  and  place  a  small  piece  of  marble 
in  the  crucible.  Now  heat  the  crucible  with  a  blast  lamp  and  aspirate 
air  slowly  through  the  apparatus.  Then  take  the  marble  out  of  the  cruci- 
ble and  aspirate  air  for  twenty  minutes  longer. 

The  potash  bulbs  and  U-tube  should  be  weighed  as  follows:  Place 
the  bulb  upon  one  balance  pan,  and  on  the  other  the  approximate  weight. 
Stand  the  U-tube  in  the  balance  case.  Close  the  door  and  do  not  open 
it  for  exactly  twelve  minutes.  Then  finish  weighing  the  bulb  so  that 
the  exact  result  is  obtained  in  fifteen  minutes  from  the  time  the  bulb 
was  placed  on  the  pan.  Now  remove  the  bulb  and  weigh  the  U-tube 
quickly. 


Fig.  92.— Portable  apparatus  for  carbon  dioxide  and  water.    Front. 

When  not  attached  in  the  train  the  U-tube  should  have  its  stop-cocks 
turned  so  as  to  close  the  openings  and  the  potash  bulb  should  be  "capped" 
with  short  pieces  of  rubber  tubing  containing,  in  one  end,  bits  of  ca- 
pillary glass  tubing. 

If  the  cement  should  contain  any  appreciable  quantity  of  carbonace- 
ous matter,  such  as  unburned  coke,  this  would  be  burned  to  carbon 


THE:    ANALYSIS    OF    CEMENT 


293 


dioxide  causing  high  results.  In  this  case  first  determine  the  carbon 
dioxide  given  off  on  ignition.  Then  weigh  another  sample  into  the 
crucible,  add  a  little  hydrochloric  acid,  filter  off  the  residue  on  ignited 


-  93.—  Portable  apparatus  for  carbon  dioxide  and  water.    Back. 


asbestos,  dry  at  100°  C.,  and  determine  the  carbon  dioxide  in  the 
residue  as  before.  This  will  represent  the  carbon  dioxide  due  to  the 
burning  of  the  organic  matter.  The  difference,  of  course,  represents 
the  carbon  dioxide  present  in  the  cement  as  carbonate. 


Fig.  94. — Clamp  for  U-tubes. 

A  U-tube,  containing  soda-lime,  may  replace  the  potash  bulb,  g.  This 
tube  should  be  similar  to  /,  and  provided  with  ground  glass  stoppers. 
About  an  inch  of  calcium  chloride  should  top  the  soda-lime  in  tht 
limb  next  the  guard  tube,  h. 


294  PORTLAND  CEMENT 

When  many  carbon  dioxide  determinations  have  to  be  made,  it  will  be 
found  convenient  to  arrange  the  apparatus  on  a  stand  as  shown  in  Figs. 
92  and  93.  Fig.  90  shows  the  front  of  the  apparatus  and  Fig.  93  the 
reverse.  The  stand  consists  of  a  wooden  base  i~y2  inches  thick,  and 
upon  this  is  mounted  an  upright  board.  At  the  end  of  this  board  and 
running  entirely  across  the  base  is  fastened  another  upright  at  right 
angles  to  the  first.  These  uprights  support  a  shelf  upon  which  rests 
the  upper  aspirator  bottle  and  the  reservoir  for  the  water-cooled  stopper. 
The  upright  nearest  the  tripod  should  be  protected  against  the  heat  of  the 
blast  lamp  by  covering  with  a  sheet  of  asbestos.  The  U-tubes,  etc.,  rest 
upon  shelves  as  shown.  The  manner  of  clamping  the  U-tubes  to  the  board 
is  also  shown  in  Fig.  94.  a'  and  a"  (Fig.  93)  are  aspirator  bottles;  b 
is  filled  with  soda-lime  and  c  with  calcium  chlorid;  d  is  Shimer's  special 
form  of  water- jacketed  platinum  crucible;  e  (Fig.  92)  is  filled  with 
calcium  chloride,  /  with  soda-lime  topped  with  calcium  chloride,  and  g 
with  calcium  chloride. 

DETERMINATION  OF  CARBON  DIOXIDE  ALONE. 

The  apparatus  just  described  for  carbon  dioxide  and  combined 
water  determinations  may,  of  course,  be  used  for  determining 
carbon  dioxide  only.  In  this  case  it  is  not  necessary  to  weigh  the 
calcium  chloride  tube,  /,  and  in  place  of  the  expensive  IT-tube 
with  its  ground  glass  stop-cocks,  a  simple  straight  form  calcium 
chloride  tube  can  be  used  just  as  well.  Neither  is  it  necessary  to 
supply  the  stopper  with  hot  water,  and  an  empty  potash  bulb  can 
replace  the  calcium  chloride  tube  c.  The  determination  is  car- 
ried out  precisely  as  if  both  the  water  and  carbon  dioxide  were 
being  considered,  with,  of  course,  the  exception  of  not  weighing 
the  tube,  f,  at  the  end  of  the  operation.  If  the  stopper  is  wet 
with  the  finger  before  insertion  into  the  crucible,  it  will  be  found 
to  go  in  easier.  This  is,  of  course,  not  permissible  when  the 
water  also  is  determined. 

Some  chemists  prefer  to  determine  carbon  dioxide  by  libera- 
ting this  constituent  with  hydrochloric  acid  and  absorbing  the 
evolved  gas  in  a  weighed  potash  bulb. 

For  carrying  out  the  determination  refer  to  the  apparatus 
(Fig.  94),  for  determining  carbon  dioxide  and  combined  water. 
Omit  the  U-tube,  c,  and  substitute  for  the  crucible,  d,  a  100  cc. 
wide  mouthed  flask  provided  with  a  funnel  tube.  Follow  the 


THE    ANALYSIS    OF    CEMENT 


295 


flask  with  a  U-tube,  containing  sulphuric  acid  (sp.  gr.  1.84)  and 
this  by  the  U-tube,  /,  the  potash  bulb,  g,  and  the  guard  tube,  h. 

A  convenient  way  of  arranging  the  apparatus  is  shown  in  Fig. 
95.     a  is  filled  with  soda-lime;  b  is  a  funnel  tube  with  ground 


Fig-  95. — Apparatus  for  determining  carbon  dioxide  by  evolution  method. 

glass  stop-cock;  c  the  100  cc.  flask;  d  contains  sulphuric  acid;  e 
and  g  calcium  chloride ;  /  is  the  weighed  potash  bulb,  and  h  the 
aspirator  bottle. 

The  Determination. 

Weigh  into  the  flask,  c,  from  2  to  4  grams  of  cement,  tritu- 
rate with  water  until  all  tendency  to  set  has  ceased,  and  connect 
the  soda-lime  tube  a  with  the  funnel  tube.  Aspirate  a  few  liters 
of  air  through  the  apparatus,  disconnect  and  weigh  the  potash 
bulb  with  attached  calcium  chloride  tube.  Again  connect  the 
apparatus,  aspirate  another  two  liters,  and  again  weigh  the  pot- 
ash bulb  and  attached  calcium  chloride  tube.  If  the  first  and 
second  weights  agree  to  within  0.0005  grams  of  each  other,  run 
into  the  flask  50  cc.  of  dilute  hydrochloric  acid  and,  if  sul- 


296  PORTLAND  CEMENT 

phides  are  present,  mix  with  this  a  very  little  chromic  acid.  After 
connecting  the  bulb  and  tube  in  the  train,  and  when  action  ceases 
apply  heat  gradually  until  the  contents  of  the  flask  boil.  Connect  the 
soda-lime  tube  a  and  aspirate  air  slowly  through  the  apparatus. 
Turn  out  the  burner  and  aspirate  two  liters  more  of  air.  Dis- 
connect the  potash  bulb  and  calcium  chloride  tube  and  weigh.  The 
gain  in  weight  is  carbon  dioxide.  Divide  the  increase  by  the 
weight  of  the  sample  used  and  multiply  the  quotient  by  100,  for 
the  percentage  of  carbon  dioxide  in  the  cement. 

RAPID  DETERMINATION  OF  CARBON  DIOXIDE. 

The  Apparatus. 

Where  a  determination  of  carbon  dioxide  has  to  be  made  only 
at  rare  intervals  and  where  great  accuracy  is  not  essential,  the 
Schrotter  apparatus  will  be  found  convenient.  It  is  shown  in 


Fig.  96. 

Fig.  96  and  is  made  of  blown  glass.  It  consists  of  a  decom- 
position flask,  C  ;  two  reservoirs,  A  and  B,  communicating  with  it 
and  a  stoppered  opening  through  which  the  sample  is  intro- 
duced into  the  flask. 

The  Determination. 

Weigh  accurately  I  gram  of  the  cement  sample  and  introduce 
into  the  flask,  C,  through  the  opening.  Stopper  the  latter, 
ffll  the  reservoir,  B,  with  dilute  (i  :  i)  hydrochloric  acid  and 
half  fill  the  second  reservoir,  A,  with  concentrated  sulphuric  acid. 
This  latter  is  intended  to  dry  the  carbon  dioxide  as  it  leaves  the 
apparatus.  Now  accurately  weigh  the  apparatus.  Allow  the 
hydrochloric  acid  to  flow  gradually  from  the  reservoir,  B,  into  the 


TH£    ANALYSIS    OF 


297 


flask  by  turning  the  stop-cock  and  removing  the  stopper  of  the 
reservoir,  B,  (not  that  of  the  flask).  As  soon  as  the  reservoir 
is  empty  replace  its  stopper.  Now  place  the  apparatus  on  a 
wire  gauze  or  hot  plate  and  heat  the  contents  until  it  just  boils. 
Open  the  stop-cock  and  remove  its  stopper,  B,  and  attach  an 
aspirator  to  the  opening  of  A.  Draw  a  slow  current  of  air 
through  the  apparatus  until  about  200  cc.  of  air  have  been  drawn 
through.  Disconnect  the  aspirator  and  allow  the  apparatus  to 
cool.  Stopper  and  weigh.  The  loss  in  weight  represents  the 
carbon  dioxide. 

The  following  apparatus  which  is  a  modification  of  Rose's  form,  may  be 
made  from  material  found  in  almost  any  laboratory.  It  is  not  so  con- 
venient, however,  as  the  above  apparatus.  It  consists  (Fig.  97)  of  a 


Pi&-  97- — Apparatus  for  rapid  determination  of  carbon  dioxide. 

small  50  cc.  Erlenmeyer  flask,  a,  provided  with  a  two  hole  rubber  stopper. 
Through  one  hole  of  this  latter  passed  a  3-inch  calcium  chloride  tube, 
b,  and  through  the  other  a  piece  of  bent  glass  tubing,  c,  one  arm  of 
which  reaches  nearly  to  the  bottom  of  the  flask,  the  other  through 
another  stopper  to  the  bottom  of  a  small  wide  tube,  d.  This  latter  is 
made  from  a  5-inch  test-tube.  Such  an  apparatus  will  weigh  from  35 


298  PORTLAND  CEMENT 

to  60  grams  according  to  the  skill  and  choice  of  materials  with  which  it 
is  made. 

Place  a  little  wool  or  cotton  in  the  bottom  of  the  calcium  chloride 
tube  and  then  fill  the  tube  with  calcium  chloride.  Next  two-thirds  fill 
the  tube,  d,  with  dilute  hydrochloric  acid,  and  weigh  into  the  flask  from 
2  to  3  grams  of  Portland  cement.  Moisten  the  cement  thoroughly  with 
water,  place  the  stopper  in  the  flask,  cap  the  openings,  o'  and  o",  with 
pieces  of  rubber  tubing  closed  at  one  end  with  bits  of  glass  rod,  and  set 
in  the  balance  case.  After  ten  minutes  weigh.  Now  attach  a  small 
guard  tube,  filled  with  calcium  chloride,  to  the  opening,  o',  and  after 
uncapping,  o",  suck  the  acid  from  the  tube,  d,  into  the  flask,  a.  As 
soon  as  the  acid  is  all  in  a,  close  o"  with  the  finger  and  cap  quickly. 
After  effervescence  ceases,  uncap  a",  attach  the  guard  tube  to  this  open- 
ing this  time,  uncap  o'  and  blow  air  gently  through  the  apparatus  for 
five  to  seven  minutes.  Cap  the  openings,  place  in  the  balance  case,  and 
after  ten  minutes  weigh.  Always,  before  weighing,  uncap  either  o'  or  o" 
for  a  few  seconds  and  then  recap.  This  allows  the  pressure,  caused  by 
the  change  of  temperature,  to  adjust  itself.  The  loss  in  weight  repre- 
sents the  carbon  dioxide,  CO2,  in  the  cement.  Divide  the  loss  by  the 
weight  of  the  sample  and  multiply  the  result  by  100  for  the  percentage. 

DETERMINATION  OF  HYGROSCOPIC  WATER. 

Weigh  5  grams  of  the  sample  upon  a  tarred  watch-glass, 
spreading  the  former  over  the  latter  in  a  thin  layer  and  dry  for 
one  hour,  (or  until  it  ceases  to  lose  weight)  at  a  temperature  of 
ioo°-iio°  C.  Cool  in  a  disiccator  and  weigh.  The  loss  in 
weight  represents  "Hygroscopic  Water"  or  "water  below  110° 
C."  or  "H2O—  no0." 

NOTES. 

Instead  of  a  watch-glass  a  weighed  platinum  or  porcelain  crucible 
or  a  weighing  bottle  may  be  used  and  a  smaller  sample  (i  gram)  taken. 

Either  of  the  two  forms  of  air-bath  described  below  will  be  found 
useful  for  drying  the  sample.  The  first  can  be  procured  of  any  dealer 
in  chemical  apparatus  and  the  second  can  be  made  from  "scraps"  around 
the  laboratory. 

The  ordinary  air-bath  consists  of  a  copper  box,  provided  with  a 
hinged  door  in  front,  and  holes  for  the  insertion  of  thermometers  and 
the  escape  of  the  water  vapor,  in  its  top.  The  box  rests  upon  iron  legs 
and  is  heated  by  a  Bunsen  burner  underneath. 

Air-baths  are  usually  provided  with  false  bottoms  of  sheet  iron  in 
order  to  prevent  the  destruction  of  the  real  one  of  copper  by  the  burner 
flame.  It  is  necessary  to  control  the  temperature  of  the  air-bath  by  a 
thermometer  inserted  through  a  cork,  in  the  opening,  in  the  top  of  the 


ANALYSIS    OF    CEMENT 


299 


oven.  The  required  temperature  can  be  maintained  by  adjusting  the 
stop-cock  of  the  gas  supply.  After  the  gas  has  once  been  regulated  the 
temperature  will  remain  constant  for  some  hours.  Gas  regulators,  called 
"thermostats,"  can  be  purchased  from  dealers  in  chemists'  supplies,  and 
while  they  are  liable  to  become  clogged  and  get  out  of  order,  they  still 
are  very  convenient  for  keeping  a  constant  temperature. 

The  author  recently  described  (in  the  Scientific  American,  vol.  Ixxx, 
p.  230)  a  form  of  drying  oven  which  he  has  used  successfully  in  his 
laboratory  for  some  years.  It  is  non-corrosive,  simple  and  cheap.  In 
the  metal  ovens,  the  acid  fumes,  given  off  in  "baking"  certain  substances, 


Fig.  98. — Glass  drying  oven. 

attack  the  metal,  forming  a  scale  which,  in  spite  of  care,  will  sooner  or 
later  drop  in  some  sample  or  dish  drying  in  the  oven.  Fig.  98  shows 
the  oven.  Select  a  large  glass  bottle  and  cut  off  the  bottom  by  making 
a  mark  on  it  with  a  file,  wrapping  two  strips  of  wet  paper,  one  a  little 
above  and  one  a  little  below  the  mark,  and  revolving  the  bottle  slowly 
and  evenly  whik  the  tip  of  a  small  blowpipe  flame  or  small  flame  from 
a  blast  lamp  plays  on  the  space  between  the  paper.  A  crack  will  start 
in  a  few  minutes,  which  will  follow  the  flame  around  the  bottle.  The 
sharp  edges  should  be  smoothed  by  a  file  dipped  in  turpentine,  and  a  nar- 
row strip  of  asbestos  wound  around  the  neck  for  a  handle.  The  upper 
half  of  the  bottle  is  placed  upon  a  sand-bath  or  hot-plate,  and  the  ob- 


3OO  PORTLAND  CEMENT 

ject  to  be  heated,  upon  a  support  of  glass  or  porcelain,  raised  above  the 
sand-bath  by  a  wire  to  form  a  tripod.  The  temperature  is  regulated 
by  a  thermometer  thrust  through  a  cork  in  the  mouth  of  the  bottle. 
Large  grooves  should  be  cut  lengthwise  along  the  cork  to  make  a  free 
escape  for  the  steam  and  vapors,  and  to  create  a  current  of  hot  air 
through  the  oven.  Both  this  and  the  other  form  of  air-bath  described 
should  be  set  in  a  corner  shielded  from  air  drafts.  If  this  is  done  the 
maintaining  of  a  constant  temperature  will  be  much  simplified. 

DETERMINATION  OF  ALKALIES. 
J.  Lawrence  Smith's  Method. 

Mix  4  grams  of  the  finely  ground  cement  with  I  gram  of  am- 
monium chloride  by  grinding  together  in  a  clean  agate  mortar 
placed  upon  a  sheet  of  black  glazed  paper.  Add  4  grams  of  cal- 
nium  carbonate,  evaporate  carefully  to  about  50  cc.,  and  add  a  little 
ilarge  platinum  crucible  provided  with. a  closely  fitting  cover.  Heat 
gently  at  first,  over  a  Bunsen  burner,  then  gradually  raise  the 
temperature  to  a  full  red  heat  and  keep  so  for  an  hour.  Cool  the 
crucible,  and  if  loose,  transfer  the  sintered  mass  to  a  small  beaker 
or  better  a  platinum  dish.  Wash  the  crucible  and  lid  with  hot 
water  and  pour  into  the  dish  or  beaker.  Digest  the  contents  of 
the  beaker  until  the  sintered  mass  slakes  to  a  fine  powder. 

If  the  sintered  mass  is  not  easily  detached  from  the  crucible, 
put  the  crucible  into  the  beaker,  add  hot  water  and  digest  with 
heat  until  the  mass  slakes.  Remove  the  crucible  and  wash  it  off 
into  the  beaker.  Now  filter  into  another  platinum  dish  or  beaker 
and  wash  the  residue  with  water.  Add  1.5  grams  of  pure  ammo- 
nium carbonate,  evaporate  carefully  to  about  50  cc.,  and  add  a  little 
more  ammonium  carbonate  and  a  few  drops  of  ammonia.  Filter 
on  a  small  filter  into  a  dish  of  platinum  or  porcelain.  Test  the 
filtrate  with  a  few  drops  of  ammonium  carbonate  solution  to 
make  sure  all  the  calcium  has  been  precipitated.  Evaporate  to 
dryness  and  ignite  at  a  barely  visible  red  until  all  the  ammonia 
salts  are  expelled  and  white  fumes  cease  to  come  off.  Cool,  dis- 
solve in  a  little  water,  add  a  few  drops  of  barium  chloride  solution, 
and  then  a  little  ammonium  carbonate  and  ammonium  oxa- 
late  solution  and  ammonia,  and  filter  from  any  residue  that  may 
form.  Add  three  or  four  drops  of  dilute  hydrochloric  acid  to  the 


THE    ANALYSIS    OF    CEMENT  3OI 

filtrate  and  evaporate  to  dryness  in  a  weighed  platinum  dish.  Ig- 
nite carefully  as  before  and  weigh  as  sodium  chloride  and  potas- 
sium chloride,  NaCl  +  KC1.  Dissolve  the  mixed  chlorides  in 
water  (they  should  be  soluble  without  residue),  and  add  to  the 
solution  an  excess  of  platiriic  chloride  solution.  Evaporate  near- 
ly to  dryness  on  the  water-bath,  add  20  cc.  80  per  cent,  alcohol  and 
let  stand  until  the  sodium  salts  dissolve.  Filter  through  a  small 
filter  and  wash  the  precipitate  by  decantation  with  80  per  cent, 
alcohol,  until  the  washings  run  through  perfectly  colorless.  Dry 
the  filter-paper  to  drive  off  the  alcohol  and  then  dissolve  the 
small  amount  of  precipitate  on  it  by  washing  with  hot  water,  al- 
lowing the  washings  to  run  into  the  weighed  dish  containing  most 
of  the  potassium  platinic  chloride  precipitate.  Evaporate  off  the 
water.  Dry  at  135°  C.,  and  weigh  as  potassium  platinic  chloride, 
K2Ptd6.  Multiply  the  weight  by  0.19384  for  potassium  oxide, 
K2O.  To  calculate  the  sodium  oxide,  multiply  the  weight  of  the 
potassium  platinic  chloride  by  0.30686  and  subtract  this  from  the 
weight  of  the  residue  of  potassium  and  sodium  chloride:  the  dif- 
ference multiplied  by  0.53028  gives  the  weight  of  the  sodium 
oxide,  Na^O. 

NOTES. 

During  the  first  part  of  the  incineration  of  the  mixture  of  cement, 
calcium  carbonate  and  ammonium  chloride  the  heat  should  be  kept  low. 
The  idea  is  not  to  volatilize  the  ammonium  chloride,  but  to  dissociate 
this  into  ammonia  and  hydrochloric  acid  by  the  heat.  The  latter  then 
unites  with  the  calcium  carbonate  to  form  calcium  chloride. 

If  the  dishes  are  removed  direct  from  the  water-bath  to  the  flame 
for  ignition  decrepitation  is  sure  to  result.  To  guard  against  this  place 
the  dish  in  the  air-bath  at  a  temperature  of  100°  C.  and  gradually  raise 
to  120°  C.,  and  then  ignite  over  a  moving  flame. 

The  heating  must  not  be  too  strong  as  potassium  chloride  is  volatile. 
To  test  its  freedom  from  ammonia  salts,  the  residue  of  mixed  chlorides, 
after  weighing,  should  be  again  heated  and  weighed,  to  see  if  further 
loss  occurs. 

This  operation  should  be  repeated  until  the  weights  are  constant. 

DETERMINATION  OF  PHOSPHORIC  ACID. 

Weigh  5  grams  of  cement  into  a  dry  beaker  and  stir  with  15 
to  20  cc.  of  water  until  all  lumps  are  broken  up.  Add  from  30  to 


302  PORTLAND 

50  cc.  of  hydrochloric  acid  (sp.  gr.  1.20)  cover  with  a  watch-glass 
and  heat  until  the  cement  is  decomposed.  Remove  the  cover, 
evaporate  to  hard  dryness  on  the  hot  plate,  and  heat  for  from 
thirty  minutes  to  one  hour  longer.  Redissolve  in  30  cc.  of  hydro- 
chloric acid  (sp.  gr.  1.20)  and  evaporate  to  pasty  consistency. 
Add  30  cc.  of  nitric  acid  (sp.  gr.  1.42)  and  evaporate  to  15  cc. 
Dilute  with  30  cc.  of  water,  heat,  filter  through  a  small  filter  and 
wash.  Add  ammonia  until  a  slight  precipitate  forms,  and  then  3 
cc.  of  concentrated  nitric  acid.  The  solution  should  now  be  am- 
ber-colored. Add  80  cc.  of  molybdate  solution,  heat  to  80°  C., 
and  stir  for  five  minutes.  Let  the  solution  stand  one  hour.  Filter 
and  wash  well  with  acid  ammonium  sulphate  solution.  Dissolve 
the  precipitate  in  the  least  possible  quantity  of  dilute  ammonia 
(1-5)  and  allow  the  solution  to  run  into  the  beaker  in  which  the 
precipitation  was  made.  Wash  the  paper  well  with  cold  water. 
The  filtrate  should  be  clear  and  colorless.  (If  cloudy  add  'hydro 
chloric  acid  until  the  liquid  is  acid,  this  usually  precipitates  the 
phosphomolybdate,  then  four  or  five  drops  of  a  concentrated  so- 
lution of  citric  acid  and  finally  ammonia  until  strongly  alkaline.) 
To  the  filtrate  add  slowly  with  constant  stirring  an  excess  of  mag- 
nesia mixture.  •  Stir  for  five  minutes,  then  add  one-third  the  vol- 
ume of  the  solution  of  strong  ammonia  and  allow  to  stand  three 
or  four  hours.  Filter,  wash  with  a  mixture  of  water  1000  cc., 
ammonia  500  cc.,  and  ammonium  nitrate  150  grams,  dry,  ignite, 
and' weigh  as  Mg2P2O7.  To  convert  this  weight  to  phosphorous 
pentoxide,  P2O5,  multiply  by  0.63780. 

NOTES. 

The  solutions  called  for  in  the  scheme  are  prepared  in  the  following 
manner : 

Molybdate  Solution:  Mix  in  a  beaker  20  grams  of  pure  molybdic 
acid  with  80  cc.  of  cold  distilled  water  and  add  16  cc.  of  ammonia  (sp. 
gr.  0.90).  When  solution  is  complete,  filter  and  pour  slowly  into  a 
mixture  of  80  cc.  of  nitric  acid  and  120  cc.  of  water. 

Ammonium  Sulphate  Solution:  Add  15  cc.  of  ammonia  (sp.  gr.  0.90) 
to  1,000  cc.  of  water  and  then  25  cc.  of  concentrated  sulphuric  acid 
(1.84  sp.  gr.). 

Magnesia  Mixture:  Dissolve  11  grams  of  crystallized  magnesium  chlo- 
ride in  water  (or  2.2  grams  of  calcined  magnesia  in  dilute  hydrochloric 
acid  avoiding  an  excess),  filter,  add  28  grams  of  ammonium  chloride, 


THE    ANALYSIS    OF    CEMENT  303 

70  cc.  of  ammonia  (sp.  gr.  0.96),  and  enough  water  to  make  200  cc. 
Filter  before  using. 

DETERMINATION  OF  MANGANESE. 
Colorimetric  Method. 

Stir  0.2  gram  of  cement  with  10  cc.  of  water  until  all  lumps  are 
broken  up,  add  10  cc.  of  dilute  ( I  :  I )  nitric  acid  and  heat  until  . 
solution  is  complete  and  all  nitrous  fumes  are  driven  off.  Now 
add  15  cc.  of  silver  nitrate  solution  (containing  1.33  gram  of 
silver  nitrate  to  the  liter  of  water).  This  will  cool  the  solution 
considerably.  Add  at  once  about  one  gram  of  ammonium  per- 
sulphate and  warm  until  the  color  commences  to  develop  and  then 
for  about  half  a  minute  longer.  Placing  the  beaker  in  coltf 
water  until  the  evolution  of  oxygen  ceases  and  then  pour  into  a 
graduated  Nessler  tube.  Into  another  cylinder  from  1-3  cc.  of  a 
standard  solution  of  manganese  (made  by  dissolving  0.0556  gram 
of  crystallized  potassium  permanganate  in  500  cc.  of  water. 
Strength  I  cc.  —  0.00005  gram  MnO)  is  measured  and  the  two 
cylinders  stood  side  by  side  and  viewed  horizontally — not  verti- 
cally. Water  is  then  added  to  the  standard  to  make  it  match 
the  other  tube.  The  height  of  the  liquid  in  the  two  tubes  is  then 
read  and  the  percentage  of  MnO  calculated  from  the  formula 

a  X  B  X  0.005 
A  X  w 

When  a  =  number  of  cc.  of  standard  solution  placed  in  the  cyl- 
inder and  A  the  number  of  cc.  to  which  it  is  diluted  in  order  to 
produce  the  same  shade  as  the  cement  sample  diluted  to  B  cc. 
W  •=.  weight  of  sample  taken  or  0.2  gram.  It  may  be  necessary 
where  the  cement  is  high  in  manganese  to  use  a  smaller  sample 
than  0.2  gram. 

DETERMINATION  OF  TITANIUM. 
Colorimetric  Method  of  A.  Weller. 

If  titanium  is  to  be  determined,  follow  closely  the  method  of 
analysis  outlined  on  page  253.  Purify  the  silica  with  hydroflu- 
oric acid  and  ignite  the  iron  and  alumina  precipitate  in  the  same 
crucible  with  the  residue  from  this  treatment.  Dissolve  the  pre- 


304  PORTLAND  CEMENT 

cipitate,  after  weighing,  in  potassium  bisulphate  by  fusion,  and 
then  the  fused  mass  in  water,  acidified  with  sulphuric  acid.  Evapo- 
rate the  fused  mass  until  fumes  of  sulphuric  acid  come  off.  Di- 
lute, filter  and  saturate  the  filtrate  with  hydrogen  sulphide  gas. 
Filter  from  any  platinum  sulphide  and  .boil  off  the  hydrogen  sul- 
phide in  a  current  of  carbon  dioxide.  Determine  the  iron  by  titra- 
tion  with  potassium  permanganate  as  described  on  page  271. 

Concentrate  the  solution,  after  the  titration  is  completed,  to 
50  cc.  and  transfer  to  a  50  cc.  Nessler  tube.  Add  2  cc.  of  3  per 
cent,  hydrogen  peroxide,  absolutely  free  from  fluorine.  This  pro- 
duces an  intense  yellow  color  which  is  proportional  to  the  amount 
of  titanium  present.  Compare  this  color  with  that  produced  by 
hydrogen  peroxide  upon  various  volumes  of  a  standard  solution 
of  titanium  prepared  as  follows :  Gently  ignite  potassium  titanic 
fluoride  and  weigh  0.6000  grams  of  this  into  a  platinum  crucible. 
Add  a  little  sulphuric  acid  and  water,  evaporate  to  dryness  and 
expel  the  acid  by  gentle  ignition.  Repeat  this  process,  and  then 
dissolve  in  a  little  concentrated  sulphuric  acid  and  dilute  to  200 
cc.  with  5  per  cent,  sulphuric  acid.  One  cc.  of  this  solution  is 
equivalent  to  o.ooi  gram  of  TiO2  or  to  0.2  per  cent,  when  a  half 
gram  sample  has  been  used.  In  comparing  the  colors  measure 
into  different  tubes  0.5,  cc.,  i.o  cc.,  1.5  cc.,  etc.,  portions  of  the 
standard  titanium  solution,  dilute  to  the  mark,  and  add  2  cc.  of 
hydrogen  peroxide  to  each.  Compare  with  the  color  produced  by 
the  sample,  making  up  new  standards  when  the  color  lies  be- 
tween two  of  the  above  tubes,  etc. 

The  method  is  accurate  to  about  o.oi  per  cent,  when  a  one-half 
gram  sample  is  taken. 


Chapter  XI. 

THE  ANALYSIS  OF  CEMENT  MIXTURES,  SLURRY,  Etc. 

Since  the  success  of  cement  making  depends  primarily  upon 
the  proper  portion  of  carbonate  of  lime  to  silica  and  alumina  in, 
the  cement  mixture,  it  is  highly  important  to  be  able  to  rapidly 
estimate  this  ratio.  If  the  materials  from  which  the  mixture  is 
made  are  of  normal  constitution  a  determination  in  it  of  the  cal- 
cium carbonate  alone  will  suffice  to  check  the  correctness  of  the 
mixture. 

For  rapidly  checking  the  percentage  of  calcium  carbonate,  two 
methods  are  in  general  use,  the  alkalimetric  method  in  which  the 
calcium  carbonate  is  decomposed  by  a  measured  quantity  of  stand- 
ard nitric  or  hydrochloric  acid  and  the  excess  of  acid  determined 
by  titration  with  standard  alkali,  and  the  indirect  gas  method  in 
which  the  carbonate  of  lime  is  decomposed  by  acid  and  the 
evolved  carbon  dioxide  gas  collected  in  a  suitable  apparatus  and 
measured ;  since  the  CO2  is  proportional  to  the  CaCO3,  the  percent- 
age of  lime  can  be  calculated  from  the  volume  of  CO2.  For  the 
latter  method  the  Scheibler's  calcimeter  is  used.  Neither  of  these 
methods  gives  very  accurate  results,  and  when  the  exact  composi- 
tion of  the  mixture  is  desired  resort  must  be  had  to  one  of  the 
longer  gravimetric  methods  given  further  on. 

In  this  country,  the  acid  and  alkali  method  is  used  almost 
exclusively  to  check  the  composition  of  the  mixture  of  raw 
materials,  while  in  England  and  Germany  the  method  in  which 
the  carbon  dioxide  is  measured  is  employed  by  most  chemists  for 
this  purpose. 

When  the  slurry  of  the  wet  process  is  analyzed  it  should  first 
be  evaporated  to  dryness,  then  finely  pulverized  in  a  mortar  and 
again  dried  for  half  an  hour  at  1 10°  C.  It  will  then  be  free  from 
moisture  and  ready  for  analysis. 

SAMPLING,  ETC. 

For  the  control  of  the  composition  of  the  mixture  of  raw  mate- 

20 


306  PORTLAND  CEMENT 

rials  it  is  usual  to  take  samples  at  certain  places  during  the  grind- 
ing. In  the  dry  process  this  is  usually  done  either  after  the  mate- 
rial leaves  the  ball  mills,  if  these  are  used  to  do  the  grinding,  or 
after  the  Griffin  mills,  if  they  are  installed  for  this  work.  Where 
tube  mills  follow  the  ball  mills  it  is  usual  to  further  check  the 
composition  of  the  raw  material  after  it  leaves  these.  The  sample 
taken  from  any  of  the  above  sources  will  need  further  grinding 
but  it  is  not  usual  to  dry  it,  unless  a  complete  analysis  is  to  be 
made.  Since  either  of  the  rapid  schemes  given  below  are  affected 
by  the  fineness  to  which  the  sample  is  ground,  it  should  be 
prepared  the  same  way  each  time,  usually  by  passing  all  of  it 
through  a  loo-mesh  test  sieve.  In  the  writer's  laboratory  the 
sample  from  the  ball  mills  is  taken  by  an  automatic  sampler  which 
will  be  described  further  on,  and  brought  to  the  laboratory  in  a 
small  tin  bucket.  The  sample  is  spread  out  on  a  piece  of  paper, 
after  a  thorough  mixing  by  rolling  back  and  forth  on  the  paper, 
and  divided  into  15-20  squares  with  the  point  of  a  spatula.  Two 
or  three  grams  are  taken  from  each  of  these  squares  and  the  main 
sample  is  then  thrown  away.  The  sample  of  from1  50-100  grams 
is  now  made  to  pass  a  loo-mesh  sieve,  using  a  large  wedgewood 
mortar  to  do  the  grinding.  The  finely  ground  sample  is  then 
mixed  and  10-20  grams  of  it  placed  in  a  coin  envelope  or  small 
bottle  and  taken  to  the  chemical  laboratory.  The  wedgewood 
mortar  answers  the  purpose  much  better  than  an  agate  one  would 
and,  with  the  soft  rock  of  the  Lehigh  District,  does  not  con- 
taminate the  sample  with  silica  to  an  amount  which  can  be  de- 
tected. 

The  following  sampler,  Fig.  99,  was  devised  by  the  writer  with 
the  assistance  of  Mr.  Owen  Hess,  Superintendent  of  the  Dexter 
Portland  Cement  Co.  It  consists  of  a  sheet  iron  cone,  of  the  dimen- 
sions shown,  having  a  rectangular  tube  inserted  at  one  point  in  its 
sides.  The  cone  slips  into  a  piece  of  four-inch  pipe  which  in 
turn  revolves  in  a  rigid  pillow  block.  The  cone  is  revolved  by  the 
bevel  gear  arrangement  shown,  which  is  run  from  one  of  the  mill 
shafts  by  a  sprocket  and  chain,  so  as  to  make  two  or  three  revolu- 
tions per  minute.  The  sampler  is  placed  below  an  overhead  screw 
conveyor  carrying  the  ground  material  from  the  ball  mills  to  the 


THE    ANALYSIS    OF    CEMENT     MIXTURES,    ETC. 


307 


tube  mill  bins.  A  hole  is  cut  in  this  conveyor  trough,  so  that  a 
stream  of  this  material  falls  into  the  cone,  striking  the  side  of 
the  latter  about  2  inches  from  the  rim.  As  the  cone  revolves  the 
material  falls  into  the  cone  and  passes  down  through  the  hollow 
shaft  into  a  pipe,  which  carries  it  back  into  the  main  elevator  or 
one  of  the  tube  mill  bins.  When,  however,  the  tube  comes  under 
the  stream,  it  is  deflected  out  of  its  course  for  a  moment  and  pass- 
ed through  this  tube  down  another  pipe  into  a  sample  bucket 
placed  at  a  convenient  place.  The  frequency  with  which  the  sam- 
ple is  taken  will  depend  on  the  number  of  revolutions  per  minute 


Fig-  99.— Automatic  sampler. 

the  cone  makes.  The  amount  will  depend  on  the  width  of  the  in- 
serted tube  and  the  circumference  of  the  cone.  The  sampler 
works  well  except  when  the  raw  material  is  very  wet  when  the 
pipes  clog  up. 

Where  samples  have  to  be  taken  from  a  belt  conveyor,  the 
appliance  shown  in  Fig.  100  will  be  found  most  reliable.  This 
sampler  was  devised  for  use  in  the  mills  of  the  Universal  Port- 
land Cement  Co.  and  has  been  in  service  for  some  years,  giv- 
ing entire  satisfaction.  It  consists  of  a  spiral,  a,  made  of  brass 


308 


PORTLAND  CEMENT 


pipe  both  ends  of  which  are  left  open.  This  spiral  is  mounted 
so  as  to  revolve  around  a  horizontal  axis,  d,  above  the  belt  con- 
veyor. The  height  of  the  axis  should  be  such  that  the  end,  b, 
of  the  spiral  just  clears  the  belt.  The  spiral  should  be  of  such 
lengtjh  and  pitch  that  one  end,  b,  will  have  its  path  in  a 
vertical  plane  passing  through  the  center  line  of  the  belt,  while 


Fig.  100. — Spiral  sampler  for  use  with  belt  conveyors. 


the  other  end,  e,  will  extend  beyond  the  conveyor,  as  shown  in 
the  illustration.  The  spiral  revolves  and  the  belt  moves  in  the 
directions  shown  by  the  arrows.  The  shaft  is  usually  run  by 
means  of  a  sprocket  on  the  shaft  and  one  on  the  idler  joined  by 
a  chain. 

When  the  spiral  revolves  and  the  belt  moves,  the  two  are  going 
in  opposite  directions.  The  end,  b,  of  course,  each  time  the 
spiral  revolves,  comes  down  close  to  the  belt  and  scoops  up 
a  little  bit  of  the  material  being  conveyed  upon  the  latter.  This 
material  is  made  to  travel  through  the  spiral  by  the  revolutions 


THE    ANALYSIS    OF    CEMENT     MIXTURES,    ETC.  309 

of  the  latter  and  is  finally  discharged  at,  e,  and  falls  through 
a  chute,  g,  into  a  sample  box,  /. 

In  hand  sampling  from  the  ball  mill,  care  must  be  taken  not  to 
get  a  false  proportion  of  fine  and  coarse  material  in  the  sample. 
The  best  place  to  sample  is  from  the  conveyor  leading  from  the 
mills,  using  a  scoop  made  by  tacking  a  piece  of  tin,  three-quarters 
of  the  way  around,  a  piece  of  board  i^  inches  square  and  8  or  10 
inches  long  as  shown  in  Fig.  101.  Never  put  the  hand  inside  a 


Fig.  loi.— Scoop  for  sampler. 

screw  conveyor  while  revolving,  as  loss  of  the  member  may  result. 
A  sample  of  cement-rock  limestone  mixture,  after  leaving  the 
mills,  will  usually  contain  from  0.05  to  0.3  per  cent,  moisture, 
so  that  for  control  and  check  purposes  drying  of  the  sample  seems 
unnecessary. 

In  the  wet  process,  the  analytical  methods  for  checking  the 
composition  of  the  slurry  are  practically  the  same  as  in  the  dry, 
but  on  the  other  hand,  the  sampling  can  not  be  done  the  same  way 
and  the  sample  itself  must  be  freed  from  a  large  amount  of  water 
from  the  mixing  pits,  and  also  after  the  slurry  has  passed  through 
the  tube  mills,  either  from  the  discharge  of  the  mill  itself  or  else 
from  the  slurry  pits. 

The  methods  of  sampling  employed  by  the  chemists  at  the 
various  mills  differ  as  the  following  will  show: 

Mr.  W.  H.  Hitchcock  of  the  Egyptian  Portland  Cement  Co., 
took  samples  from  the  mixing  pit,  by  means  of  a  pint  cup,  fasten- 
ed to  the  end  of  a  wooden  pole  by  means  of  a  wire.  It  is  put  in 
the  slurry  bottom  side  up,  pushed  down  to  the  required  depth, 
about  the  middle  of  the  pit,  and  drawn  up.  As  the  pole  is  pulled, 
the  cup  rights  itself  and  fills.  Each  pit  holds  170  cu.  yds.  and  is 
sampled  in  20  places.  The  sample  is  then  put  in  a  miniature  tube 
mill  and  ground  for  10  minutes.  From  25-35  grams  of  this 
sample  are  spread  on  a  thin  piece  of  cardboard  and  dried  at 
100°  C.,  after  which  it  is  ground  in  an  agate  mortar  when  it 
is  ready  for  the  check  determinations. 


3io 


PORTLAND  CEMENT 


Mr.  N.  S.  Potter,  Jr.,  of  the  Peninsular  Portland  Cement  Co., 
takes  his  sample  from  the  slurry  tanks,  which  are  16  ft.  deep,  by 
means  of  a  two-quart  tin  pail,  attached  to  the  end  of  a  pole  by  a 
common  harness  snap.  The  pail  is  pushed  down  into  the  slurry, 
bottom  up,  and  full  of  air.  At  the  desired  point  the  pole  is  given 
a  slight  jerk  when  the  pail  rights,  allow  the  air  to  escape  and 
fills  with  the  marl  or  slurry,  as  the  case  may  be.  The  sample  is 
then  spread  out  on  a  piece  of  paper  and  dried  on  the  hot-plate. 

Mr.  Frank  I.  Post,  of  the  Wolverine  Portland  Cement  Co.,  uses 
a  special  form  of  sampler,  consisting  of  a  cup  with  two  fly  valves, 
one  at  the  top  and  another  at  the  bottom,  attached  to  a  pole.  When 


Fig.  102. — Marl  sampler. 

the  sampler  is  thrust  down  through  the  slurry,  both  valves  open 
and  the  marl  simply  runs  through  the  cup,  but  when  the  sampler 
is  raised  the  valves  shut,  thus  enclosing  a  sample  in  the  cup.  In 
removing  this  sampler  from  the  tank  care  must  be  used  not  to 
lower  it  at  all.  If  this  is  done,  the  valves  of  course,  open  and 
the  sample  previously  taken  is  lost,  and  in  its  place  will  be  a 
new  sample  from  the  point  of  lowering. 

Fig.   1 02  shows  a  marl  sample  of  the  above  order  described 
in  The  Cement  Record.     It  is  made  of  tin  and  the  top  is  held 


THE)    ANALYSIS    OF     CEMENT     MIXTURES,     ETC.  31 1 

in  place  by  a  bayonet  catch.  Flap  valves  are  fastened  to  the 
top  and  bottom  by  hinges,  the  former  opens  outward  and  the 
latter  inward.  It  is  used  as  described  above. 

Mr.  Homer  C.  Lask,  of  the  Omega  Portland  Cement  Co.,  also 
makes  use  of  a  bucket  with  a  valve  in  sampling  marl.  His  appa- 
ratus consists  of  a  heavy  iron  bucket,  three  inches  in  diameter 
and  nine  or  ten  inches  long.  It  has  a  valve  in  the  bottom,  which 
opens  as  the  bucket  sinks  through  the  marl,  but  closes  as  soon  as 
it  is  started  in  the  opposite  direction.  A  sample  can  thus  be  taken 
at  any  depth  desired.  The  sampler  is  attached  to  a  rope  and 
sinks  into  the  marl  by  its  own  weight.  It  is  withdrawn  by  means 
of  a  small  windlass.  From  three  to  five  samples  are  taken  from 
a  tank,  the  different  samples  mixed  together,  and  the  whole  taken 
as  the  tank  sample. 

The  slurry  is  sampled,  automatically,  as  it  leaves  the  tube  mill 
by  an  ingenious  device.  The  tube  mills  at  this  plant  have  a  cen- 
tral discharge  and  on  the  inner  surface  of  the  discharge  conduit 
is  attached  a  stout  cup,  of  about  I  cu.  in.  capacity,  with  its  open 
end  towards  the  stream  of  slurry  as  the  mill  makes  its  revolu- 
tion. The  cup  fills  as  it  passes  through  the  stream  of  slurry  and 
discharges  as  it  is  carried  over  the  top.  A 'portion  of  the  dis- 
charge is  allowed  to  fall  into  a  small  trough,  down  which  it  flows 
into  a  bucket.  This  bucket  holds  about  four  pints  and  the  sam^- 
pler  is  so  gauged  that  the  former  will  fill  in  about  an  hour. 

Samples  of  slurry  and  marl  may  also  be  taken  by  agitating  the 
vat  or  tank  thoroughly  and  then  taking  two  or  three  small  sam- 
ples from  the  elevator  or  pump  discharge,  and  mixing  and  grind- 
ing the  sample  obtained.  In  order  to  correct  the  composition  of 
slurry  found  to  be  under  or  overclayed,  it  is  necessary  to  know  not 
only  how  much  carbonate  of  lime  it  contains,  but  also  how  much 
water.  To  determine  the  latter  the  usual  rule  is  to  evaporate  a 
weighed  portion  of  the  slurry  to  dryness  and  determine  the  loss  in 
weight.  This  evaporation  can  be  carried  on  most  rapidly  and  also 
safest  in  the  "radiator."  This  consists  of  a  round  sheet  iron  box, 
with  an  open  top  and  bottom  flanged  on.  It  is  made  of  any  conven- 
ient dimensions  and  usually  with  its  diameter  at  the  top  a  little 


312  PORTLAND  CEMENT 

larger  than  at  the  bottom.  Convenient  dimensions  are  6  inches  deep, 
5^2  inches  diameter  at  the  top  and  4^2  inches  diameter  at  the 
bottom.  The  radiator  will  then  set  in  the  ring  of  a  five-inch  tri- 
pod. The  substance  to  be  evaporated  is  held  on  a  triangle  sup- 
port, midway  between  the  top  and  bottom  of  the  box  and  made 
of  heavy  copper  or  iron  wire.  Fig.  103  shows  the  apparatus, 
which  is  to  be  heated  by  a  burner. 

Practically  the  same  results  can  be  arrived  at  by  using  a  round 
sheet  iron  cylinder,  6  inches  high  and  5  inches  in  diameter  with  a 
support  3  inches  from  the  bottom,  and  setting  over  the  hottest 
part  of  the  hot-plate. v  An  ordinary  porcelain  dish  may  be  mada 
use  of  to  hold  the  sample  but  a  flat  dish  of  tin  or  aluminum  will 


Fig.  103. — Radiator  for  drying  slurry  samples. 

serve  the  purpose  better.  Not  only  because  greater  surface  is  ex- 
posed but  also  because  metal  is  a  better  conductor  of  heat  than 
porcelain.  As  a  quick  test  to  determine  when  all  the  water  is 
driven  off,  hold  a  cold  watch-glass  over  the  dish  and  observe  if 
any  moisture  collects  on  it.  If  16.88  cc.  of  slurry  are  taken  for 
evaporation  each  o.oi  gram  of  dried  residue  will  represent  the 
number  of  pounds  of  dried  slurry  in  a  cubic  yard  of  the  wet 
slurry.  This  amount  may  be  measured  by  means  of  a  small 
pipette  made  to  hold  exactly  this  amount  to  the  mark.  In  use 
the  pipette  must  be  washed  out  with  a  jet  of  water  from  a  wash- 
bottle.  Or  168.8  cc.  may  be  taken  when  o.i  gram  will  represent 
pounds  per  cu.  yard,  etc.  When  organic  matter  is  present  this1 
also  acts  as  a  disturbing  element  in  determining  the  correctness 
of  the  composition  of  the  slurry.  If  constant,  allowance  can 
usually  be  made  for  it,  but  when  variable  the  best  plan  is  either 


THE    ANALYSIS    OF    CEMENT    MIXTURES,    ETC.  313 

to  burn  this  off  or  else  run  the  mix  by  a  ratio  of  lime  to  in- 
soluble.1 

Mr.  A.  Lundteigen,  of  the  Peerless  Portland  Cement  Co.,  weighs 
the  dried  sample  into  a  small  iron  tray,  which  is  suspended  in  a 
larger  one  and  this  in  its  turn  is  covered  and  put  over  a  good 
Bunsen  burner  for  20  minutes.  In  this  way  over  three-quarters 
of  the  organic  matter  is  driven  off  without  decomposing  the 
carbonate.  This  also  puts  the  sample  in  such  a  condition  that 
it  will  sink  in  a  solution  of  hydrochloric  acid,  and  be  quickly  dis- 
solved. Without  this  baking  process  the  marl  used  By  this  com- 
pany will  float  on  top  of  the  acid  and  even  shaking  and  boiling 
will  dissolve  it  only  with  difficulty.  The  baked  sample,  however, 
is.  very  hygroscopic  and  takes  up  moisture  rapidly  from  the  air, 
so  it  must  be  weighed  quickly. 

RAPID  METHODS  FOR    CHECKING   THE   PERCENTAGE   OF 

CALCIUM  CARBONATE  IN   CEMENT  MIXTURES. 

By  Standard  Acid  and  Alkali. 

Phenolphthalein. 
Dissolve  i  gram  of  phenolphthalein  in  100  cc.  of  alcohol   (50 


Fig.  104.— Phenolphthalein  dropper. 

per  cent).     Keep  in  a  small  bottle  provided  with  a  perforated 
stopper  through  which  passes  a  small  pipette,  made  from  a  piece 

i  See  Chapter  IV. 


314  PORTLAND  CEMENT 

of  5  inch  narrow  bore  glass  tubing  by  drawing  out  one  end  to  a 
fine  opening,  and  blowing  a  bulb  in  the  other,    Fig.   104. 
One  drop  of  this  solution  is  sufficient  for  a  determination. 

Standard  Alkali. 

In  order  to  prepare  standard  alkali  of  exactly  %  N  strength 
it  is  necessary  to  first  prepare  a  standard  solution  of  some  acid, 
preferably  of  sulphuric,  because  of  the  ease  with  which  this  can 
be  standardized  by  precipitation  with  barium  chloride.  To  pre- 
pare this  standard  acid,  measure  out  with  a  burette  11.2  cc.  of 
concentrated  sulphuric  acid  (1.84  sp.  gr.)  and  dilute  to  one  liter. 
Shake  well  and  measure  into  each  of  two  small  beakers  10  cc.  of 
this  sulphuric  acid  and  dilute  to  100  cc.  Add  a  few  drops  of 
hydrochloric  acid,  heat  to  boiling,  and  precipitate  the  sulphuric 
acid  with  barium  chloride.  Let  the  precipitate  stand  over  night, 
then  filter  through  a  double  filter  (or  preferably  the  Shinier  fil- 
ter1), wash  with  hot  water,  ignite  and  weigh.  Calculate  the  quan- 
tity of  this  acid  equivalent  to  10  cc.  of  %  N.  sulphuric  acid  in  the 
following  manner.  Ten  cc.  of  %»N.  sulphuric  acid  should  give 
0.467  grams  of  BaSO4.  If  the  average  weight  of  both  precipitates 
is  a  gram,  then  letting  x  represent  the  number  of  cubic  centi- 
meters containing  0.467  grams  of  BaSO4. 

4.67 

0.467  :  a  :  x  :  10  or  x  — 

a 

Hence  zi_Zcc<  of  our  standard  acid  will  be  equivalent  to  10  cc. 

of  ^5  N.  acid.  This  should  be  marked  on  the  bottle  and  the  solu- 
tion put  away  in  a  dark  cool  place  for  use  at  some  future  time. 
To  prepare  the  standard  alkali,  dissolve  175  grams  of  caustic 
soda  in  eight  liters  of  distilled  water  in  a  two  gallon  bottle  (which 
usually  holds  9  liters)  and  mix  well  by  shaking.  Now  measure 
into  each  of  two  beakers  the  quantity  of  our  standard  sulphuric 
acid  equivalent  to  10  cc.  of  normal  acid,  and  after  adding  a  drop 
of  phenolphthalein  solution,  run  in  the  sodium  hydroxide  solution 
from  a  burette  until  the  solution  turns  purple  red.  The  two  titra- 
tions  should  check  exactly.  If  not,  repeat  until  they  do.  Now 

1  See  page  286. 


THE    ANALYSIS    OF    CEMENT    MIXTURES,    ETC.  315 

dilute  the  caustic  soda  solution  so  that  it  is  exactly  2/5  Normal. 
The  number  of  cubic  centimeters  of  water  necessary  to  add  to 
the  caustic  soda  solution  may  be  found  by  the  formula 


-  x  c 


when  b  =  cc.  soda  required  to  neutralize  the  equivalent  of  10  cc. 
of  ^5  N.  acid  and  C  =  quantity  of  caustic  soda  solution  still  left 
in  the  bottle. 

Example  of  the  preparation  of  the  standard  2/5  N.  alkali. 

Weight  of   ist  BaSO*  precipitate    0.4975 

Weight    of    2d    BaSO*   precipitate    0.4987 

Average    0.4981 

nM-         r  4  6?O 

Therefore  *'   '    ^  =9.38  cc.  of  the  acid,  are  equivalent  to  locc. 

of2/5N  acid. 

Now  9.38  cc.  of  the  above  acid  require  8.7  cc.  of  caustic  soda,  as  de- 
termined by  duplicate  titrations.  As  we  have  used  20  cc.  of  our  caustic 
soda  we  will  have  in  the  bottle  8,000  —  20  =  7,980  cc.  and  hence  we 

(10  \ 

•g-—  —  i  J   7, 980  or  1,189  cc'     Since  our  bottle  will  only 

hold  9  liters  it  will  probably  be  better  to  draw  off  exactly  i  liter  when  the 

Cio  \ 

g— - — i    J    6,980  or  1,040  cc. 

We  therefore  measure  out  this  quantity  of  water  and  add  it  to  the  con- 
tents of  the  bottle. 

The  standard  caustic  soda  solution  should  now  be  checked  against 
the  acid  and,  if  not  of  correct  strength,  water  must  be  added,  as  indi- 
cated, until  it  is  exactly  2/5  N.  strength. 

One  cc.  of  this  solution  is  equivalent  to  exactly  0.020  grams  of  CaCO3, 
or  2.0  per  cent,  where  a  one  gram  sample  is  used.  A  two  gallon  bottle 
of  standard  alkali  will  make  at  least  2,000  determinations  so  it  pays  to 
make  it  of  correct  strength  and  save  calculations. 

Standard  Acid. 

Take  the  specific  gravity  of  a  bottle  of  hydrochloric  acid,  using 
a  hydrometer  for  the  purpose.  Refer  to  the  table  of  specific 
gravities  of  hydrochloric  acid  given  below  and  calculate  from  this 
the  quantity  of  acid  necessary  to  contain  97.0  grams  of  HC1. 

Measure  this  quantity  of  the  acid  into  a  liter  flask  and  dilute  to 
the  mark,  pour  into  an  eight  liter  bottle  and  add  seven  liters  of 


PORTLAND  CEMENT 


water,  measuring  with  the  flask.  Mix  the  contents  of  the  bottle 
well  by  shaking.  Ten  cc.  of  this  solution  should  be  equivalent  to 
from  8-1  to  8-5  cc.  of  the  %  N.  alkali  when  checked  by  adding  a 
drop  of  phenolphthalein  solution  and  running  in  the  alkali  to  a 
purple  red  color.  If  its  value  does  not  lie  between  these  figures 
add  acid  or  water  to  make  it  of  this  strength. 

TABLE  XX. — SPECIFIC  GRAVITIES  OF  HYDROCHLORIC  ACID. 


Sp.  gr.  at 

15°  c. 

Degrees 
Baume 

Degrees 
Twadd'l 

Per  cent, 
of  HC1. 

Grams  of  HC1. 
in  i  liter. 

Correction  of 
the  sp.  gr. 
for  ±  i  °C. 

.005 

0.7 

I 

1.  12 

11.32 

0.0006 

.OIO 

1.4 

2 

2.12 

21.43 

0.0006 

.015 

2.1 

3 

3-12 

31.67 

0.0006 

.020 

2.7 

4 

4.11 

4L99 

0.0006 

.025 

34 

5 

5-  II 

52-41 

0.0006 

.030 

4-i 

6 

6.II 

62.93 

0.0006 

•035 

4-7 

7 

7.10 

73-55 

0.0006 

.040 

5-4 

8 

8.10 

84-27 

0.0006 

•045 

6.0 

9 

9.10 

95-09 

0.0006 

.050 

6.7 

10 

10.09 

106.01 

0.0006 

•055 

7-4 

ii 

11.09 

117.02 

0.0006 

.060 

8.0 

12 

12.09 

128.14 

0.0006 

.065 

8-7 

13 

13.08 

139.36 

0.0006 

.070 

9-4 

14 

14.08 

150.68 

0.0006 

•075 

10.0 

15 

15.08 

162.10 

0.0006 

.080 

10.6 

16 

16.07 

173-63 

0.0006 

.085 

II.  2 

17 

17.07 

185.24 

0.0006 

.090 

11.9 

18 

18.07 

196.96 

0.0006 

.095 

12.4 

19 

19.07 

208.78 

0.0006 

.100 

13.0 

20 

20.06 

220.70 

0.0006 

.105 

13-6 

21 

2  1.  06 

232.68 

0.0006 

.110 

14.2 

22 

22.06 

244.80 

0.0006 

.115 

14.9 

23 

23.05 

257.02 

0.0006 

.120 

15.4 

24 

24.05 

269.34 

0.0006 

•125 

16.0 

25 

25.05 

281.76 

0.0006 

.130 

16.5 

26 

26.04 

294.28 

0.0006 

•135 

17.1 

27 

27.04 

306.90 

*o.ooo6 

.140 

17.7 

28 

28.04 

319-62 

0.0006 

•145 

18.3 

29 

29.03 

332.44 

0.0006 

.150 

18.8 

30 

30.03 

345.36 

0.0006 

•155 

19-3 

31 

31.03 

358.34 

0.0006 

.160 

19.8 

32 

32.02 

371.44 

0.0006 

.165 

20.3 

33 

33-02 

384.64 

0.0006 

.170 

20.9 

34 

34-02 

397-94 

0.0006 

•175 

21.4 

35 

35-01 

411-34 

0.0006 

.180 

22.  0 

36 

36.01 

424.84 

0.0006 

.185 

22.5 

37 

37-01 

438.44 

0.0006 

.190 

23.0 

38 

38.01 

452.H 

0.0006 

•195 

23.5 

39 

39-00 

466.00 

0.0006 

.200 

24.0 

40 

40.00 

479.84 

0.0006 

THE)    ANALYSIS    OF    CEMENT    MIXTURES,    ETC.  317 

Example  of  the  preparation  of  the  standard  acid. 

On  testing  a  bottle  of  hydrochloric  acid  its  specific  gravity  is  found 
to  be  1.195°  C.  at  23°  C.  Correcting  this  to  15°  C.  we  have  1.95  + 
(23  —  15)  X  0.00006  =  1.1998,  or  practically  1.20  sp.  gr.  at  15°  C.  Hy- 
drochloric acid  of  i. 20  sp.  gr.  contains  479.84  grams  of  HC1  per  liter 

or  0.480  grams  per  cubic  centimeter.  Therefore  — ?^ —  or  202  cc.  will  con- 
tain 97  grams  of  HC1,  hence  we  measure  out  this  quantity  of  acid  and  dilute 
to  eight  liters. 

Standard  Sample. 

A  standard  sample  of  the  raw  material  is  necessary  to  stand- 
ardize the  acid  and  alkali  for  actual  use.  This  sample  should  be 
ground  in  the  same  manner  as  the  daily  run  of  samples  to  be 
checked  by  the  acid  and  alkali.  It  should  all  pass  a  loo-mesh 
sieve  and  be  freed  from  hygroscopic  moisture,  by  drying  for  some 
hours,  at  110°  C.  Three  of  four  pounds  of  this  sample  should 
be  prepared  and  kept  in  air-tight  jars  or  bottles.  A  small  sample 
(one  or  two  ounces)  of  this  should  be  placed  in  a  two  ounce  bot- 
tle and  stoppered  with  a  rubber  cork  when  not  in  use.  This  small 
sample  can  then  be  re-dried  for  an  hour  at  ioo°-iio°  C.  and  used 
for  standardizing,  avoiding  the  frequent  opening  and  mixing  of 
the  contents  of  the  large  jars  or  bottles. 

After  drying,  the  standard  sample  should  be  carefully  analyzed. 
It  should  contain  approximately  the  quantity  of  carbonate  of 
lime  which  it  is  desired  to  have  in  the  mix,  and  the  amount  of 
magnesia  should  also  be  normal.  When  the  magnesia  varies  at 
different  times  fresh  standard  samples  should  be  prepared  to  con- 
tain these  varying  percentages  of  magnesia;  otherwise  the  lime 
will  be  reported  too  high. 

Standardising  the  Acid. 

Weigh  one  gram  of  the  standard  sample  into  a  600  cc.  Erlen- 
meyer  flask  and  run  in  from  a  pipette  50  cc.  of  standard  acid. 
Close  the  flask  with  a  rubber  stopper,  having  inserted  through 
it  a  long  glass  tube  30  inches  long  and  about  %-inch  internal 
diameter.  Heat  the  flask  on  a  wire  gauze  over  a  burner  as  shown 
in  Fig.  105  until  steam  just  begins  to  escape  from  the  upper  end  of 
the  tube.  The  heating  should  be  so  regulated,  that  the  operation 


PORTLAND  CEMENT 


requires  very  nearly  two  minutes,  from  the  time  the  heat  is 
applied,  until  steam  issues  from  the  tube.  Remove  the  flask  from 
the  heat,  as  soon  as  the  steam  escapes  from  the  tube,  and  rinse 
the  tube  into  the  flask,  in  the  following  manner.  Rest  the  flask, 
still  stoppered,  on  the  table  and  grasp  the  tube  between  the 
thumb  and  forefinger  of  the  left  hand.  Direct  a  stream  of  cold 
water,  from  a  wash-bottle  in  the  right  hand,  down  the  tube,  hold- 
ing the  latter  inclined  at  an  angle  45°,  and  rolling  the  flask  from 
side  to  side  on  the  table,  in  sweeps  of  two  or  three  feet,  by  twirl- 


Fig.  105.— Apparatus  for  determining  calcium  carbonate  with  acid  and  alkali. 

ing  the  tube  between  the  finger  and  thumb.  Unstopper  the  flask 
and  rinse  off  the  sides  and  bottom  of  the  stopper,  into  the  flask, 
and  wash  down  the  sides  of  the  latter.  Add  a  drop  or  two  of 
phenolphthalein  and  run  in  the  standard  alkali,  from  a  burette, 
until  the  color  changes  to  purple  red.  This  color  is  often  ob- 
scured until  the  organic  matter  settles,  so  it  is  necessary  to  hold 
the  flask  to  the  light  and  observe  the  change  by  glancing  across 
the  surface.  A  little  practice  will  easily  enable  the  operator  to 
carry  on  the  titration  with  accuracy  and  precision. 

If  the  standard  sample  contains  L  per  cent,  carbonate  of  lime 


THE;    ANALYSIS    OF    CEMENT     MIXTURES,    ETC. 


319 


and  d  cc.  of  alkali  are  required  to  produce  the  purple  red  color, 
then  to  find  the  carbonate  of  lime  in  other  samples  it  is  only  nec- 
essary to  subtract  the  number  of  cubic  centimeters  of  alkali  re- 
quired in  their  case  from  d,  multiply  the  difference  by  2  and  add 
to  L  for  the  percentage  of  carbonate  of  lime  in  them;  or  the 
number  of  cc.  is  greater  than  d,  subtract  d  from  this  number,  mul- 
tiply by  2  and  subtract  from  L  for  the  carbonate  of  lime. 

In  order  to  avoid  all  calculations  prepare  a  table  giving  the 
various  percentages  of  carbonate  of  lime  corresponding  to  differ- 
ent quantities  of  alkali. 

Example  of  Such  a  Table :  Suppose  the  standard  sample  contains 
75.0  per  cent,  carbonate  of  lime  and  4.6  cc.  of  standard  alkali  are  re- 
quired to  produce  a  purple  red  color.  Then  since  each  cc.  of  alkali 
is  equivalent  to  0.02  grams  or  2  per  cent,  of  carbonate  of  lime  4.5  cc. 
alkali  would  represent  75.2  per  cent,  carbonate  of  lime  and  4.4  cc.  alkali 
would  be  equivalent  to  75.4  per  cent,  carbonate  of  lime.  Similarly  4.7 
cc.  alkali  are  equal  to  74.8  per  cent,  carbonate  of  lime.  So  we  see  the 
lime  progresses  by  0.2  per  cent,  for  each  decrease  of  o.i  cc.  alkali  and 
we  can  quickly  write  the  following  table : 


Cc. 
alkali 

Per  cent. 
CaCO3. 

Cc. 
alkali 

Per  cent. 
CaCO3. 

Cc. 

alkali 

Per  cent 
CaCO3. 

3-8 

76.6 

4-5 

75-0 

5.2 

738 

3-85 

76.5                 4-55 

75-1 

5-25 

73-7 

3-9 

76.4 

4-6 

75-0 

5-3 

73.6 

3-95 

76.3 

4-65                   74-9 

5-35 

73-5 

4.0 

76.2 

4-7                   74-8 

5-4 

73-4 

4-05 

76.1 

4-75 

74-7 

5-45                 73-3 

4.1 

75-0 

4.8 

74-6 

5-5                  73.2 

4.15 

75-9 

4.85 

74.5 

5-55                73-i 

4.2 

75-8 

4-9 

74-4 

5-6                   73-o 

4.25 

75-7 

4-95 

74-3 

5.65 

72-9 

4-3 

75.6 

5.0                  74.2 

5-7                   72.8 

4-35 

75-5 

5-0 

74.i 

5.75                 72.7 

4.4 

75-4 

5-1                  74.o 

5-8                  72.6 

4-45 

75-3 

5-15 

72-9 

5.85 

72.5 

Determination. 

Weigh  I  gram  of  the  sample,  which  has  been  ground  to  pass  a 
loo-mesh  sieve,  into  the  flask,  add  50  cc.  of  the  standard  acid  and 
proceed  as  directed  under  standardizing  the  acid.  The  percent- 
age of  carbonate  of  lime  may  be  found  from  the  number  of  cc. 


320  PORTLAND  CEMENT 

of  alkali  used  either  from  the  preceding  table  or  by  the  formula 

%  CaC03  =  L  +  (d  —  S)   X  2 

Where  L  and  d  have  the  same  values  as  in  the  paragraph  on 
"Standardizing  the  Acid"  and  S  represents  the  number  of  cubic 
centimeters  -required  for  the  sample  whose  composition  is  de- 
sired. If  4.25  ^c.  of  alkali  are  required  then  the  sample  contains 
75  -j-  (4.6  —  4.25)  X  2  =  75.7  per  cent,  carbonate  of  lime. 

NOTES. 

The  process  depends  upon  the  decomposition  of  calcium  carbonate 
by  a  measured  quantity  of  standard  alkali  in  excess  of  that  required  by 
theory  and  then  determining  the  excess  acid  by  titration  with  standard 
alkali. 

CaCOs  +  2HC1  =  CaCl2  +  H2O  +  CO2. 

100.1  36.45 

HC1  +  NaOH  =  NaCl  +  H2O. 
36.45         40.05 

Hence,  I  cc.  of  2/5  normal  acid  will  decompose  0.02  grams  of  CaCOs 
and  i  cc.  of  2/r  normal  acid  will  neutralize  as  much  acid  as  0.02  grams 
of  CaCO3. 

Phenolphthalein  is  a  very  delicate  indicator.  It  is,  however,  very  sus- 
ceptible to  carbon  dioxide  and  the  solution  must  be  freed  from  the 
latter  by  boiling  whenever  this  indicator  is  used.  It  is  also  useless  in 
the  presence  of  free  ammonia  or  its  compounds.  The  addition  of  a  few 
drops  of  the  indicator  to  an  acid  or  neutral  solution  shows  no  color, 
but  the  faintest  excess  of  caustic  alkali  gives  a  sudden  change  to  purple 
red.  Methyl  orange  may  be  used  in  place  of  phenolphthalein.  While  not 
so  delicate  it  possesses  certain  advantages  over  the  latter.  It  can  be  used 
in  the  cold  with  carbonates,  and  its  delicacy  is  not  impaired  by  the 
presence  of  ammonia  or  its  salts.  A  convenient  strength  for  the  methyl 
orange  indicator  is  o.i  gram  of  the  salt  to  100  cc.  of  water.  One  drop 
of  this  solution  is  sufficient  for  100  cc.  of  any  colorless  solution.  Alkaline 
liquids  are  fairly  yellow  with  methyl  orange  and  acid  ones  are  pink 
Of  the  two  indicators,  however,  phenolphthalein  is  much  to  be  pre- 
ferred for  this  work,  as  the  carbon  dioxide  has  all  been  boiled  off  the 
acid  and  provided  the  alkali  is  properly  kept,  the  amount  in  this  is 
constant  and  hence  exercises  the  same  influence  all  the  time. 

Standard  2/5  N  caustic  soda  may  be  prepared,  however,  free  from 
carbon  dioxide,  by  the  following  method :  Take  about  twice  the  quan- 
tity of  caustic  soda  required  for  the  standard  solution,  dissolve  in  water 
and  add  25  grams  of  freshly  slaked  lime  made  into  a  milky  paste  with 
water.  Boil  for  10  or  15  minutes  and,  when  cool  enough  to  avoid 
cracking  the  latter,  pour  into  a  five  pint  bottle.  Add  water  enough  to 


THE    ANALYSIS    OF    CEMENT     MIXTURES,     ETC.  321 

nearly  fill  the  bottle,  stopper,  shake  and  let  stand  over  night  to  settle. 
In  the  morning,  siphon  off  the  clear  liquid  and  make  up  to  five  or  six 
liters.  Run  against  the  standard  sulphuric  acid  solution  and  dilute  as 
directed  above  for  the  preparation  of  2/_  N  alkali. 

As  a  preliminary  standard  for  the  preparation  of  the  2/5  N  alkali, 
hydrochloric  acid  may  be  used  instead  of  sulphuric  acid.  It  is  more 
troublesome  to  standardize,  however.  Prepare  the  2/5  normal  hydro- 
chloric acid  as  directed  in  the  scheme  and  standardize  gravimetrically 
as  follows: 

To  any  convenient  quantity  of  the  acid  to  be  standardized,  add  solu- 
tion of  silver  nitrate  in  slight  excess,  and  2  cc.  pure  nitric  acid  (sp.  gr. 
1.2).  Heat  to  boiling-point,  and  keep  at  this  temperature  for  some 
minutes  without  allowing  violent  ebullition,  and  with  constant  stirring, 
until  the  precipitate  assumes  the  granular  form.  Allow  to  cool  some- 
what and  then  filter  through  asbestos.  Wash  the  precipitate  by  de- 
cantation,  with  200  cc.  of  very  hot  water,  to  which  has  been  added  8 
cc.  of  nitric  acid  and  2  cc.  of  dilute  solution  of  silver  nitrate  contain- 
ing i  gram  of  the  salt  in  100  cc.  of  water.  The  washing  by  decantation 
is  performed  by  adding  the  hot  mixture  in  small  quantities  at  a  time, 
beating  up  the  precipitate  well  with  a  thin  glass  rod  after  each  addi- 
tion. The  pump  is  kept  in  action  all  the  time ;  but  to  keep  out  dust 
during  the  washing,  the  cover  is  only  removed  from  the  crucible  when 
the  fluid  is  to  be  added. 

Put  the  vessels  containing  the  precipitate  aside,  return  the  washings 
once  through  the  asbestos  so  as  to  obtain  them  quite  clear,  remove  from 
the  receiver,  and  set  aside  to  recover  the  silver.  Rinse  the  receiver 
and  complete  the  washing  of  the  precipitate  with  about  200  cc.  of  cold 
water.  Half  of  this  is  used  to  wash  by  decantation  and  the  remainder 
to  transfer  the  precipitate  to  the  crucible  with  the  aid  of  a  trimmed 
feather.  Finish  washing  in  the  crucible,  the  lumps  of  silver  chloride 
being  broken  down  with  a  glass  rod.  Remove  the  second  filtrate  from 
the  receiver  and  pass  about  20  cc.  of  alcohol  (98  per  cent.)  through  the 
precipitate.  Dry  at  from  140°  to  150°.  Exposure  for  half  an  hour  is 
found  more  than  sufficient  at  this  temperature,  to  dry  the  precipitate 
thoroughly.  The  weight  of  silver  chloride  multiplied  by  0.25424  gives 
the  hydrochloric  acid  in  the  volume  taken. 

Instead  of  2/5  normal  caustic  soda  the  corresponding  2/5  normal  caustic 
potash  may  be  used.  To  prepare,  substitute  220  grams  of  KOH  for  175 
grams  of  NaOH,  and  proceed  as  directed  in  the  scheme. 

The  standard  hydrochloric  acid  used  in  the  determination  itself  is  not 
exactly  2/5  normal;  in  fact,  is  much  weaker  than  this.  It  is  made  so 
in  order  to  avoid  waste  of  the  alkali.  If  made  a/5  normal  strength,  it 
would  require  about  12.5  cc.  of  alkali  to  titrate  back.  A  smaller  pipette 
might  be  used  or  the  acid  measured  with  a  burette.  The  automatic 
pipettes  are  usually  made  in  sizes,  25  cc.,  50  cc.,  etc.,  and  are  so  con- 
21 


322 


PORTLAND  CEMENT 


venient  for  measuring  the  acid  that,  as  there  is  nothing  to  be  gained  by 
making  the  acid  2/5  normal  strength,  it  will  be  found  more  convenient 
to  make  it  of  the  strength  indicated  in  the  scheme,  and  use  a  50  cc. 
automatic  pipette. 

In  some  laboratories,  the  acid  and  alkali  are  both  made  of  V5  N 
strength  and  a  half  gram  sample  is  used  for  the  determination.  There 
appears  to  be  nothing  gained  by  this  and  something  may  be  lost  as  the 
stronger  acid  is  a  better  solvent  for  the  sample. 

The   bottle   of   strong  hydrochloric    acid,   used   to    make   the    standard 


.    .,  Fig.  106. — Stand  for  acid  and  alkali  bottles  and  pipettes.    - 

acid,  should  be  marked  with  the  number  of  cubic  centimeters  required 
to  make  eight  liters  of  standard  acid  and  put  away  for  use  in  making 
up  the  next  lot  of  acid: 

In    preparing   a   second    lot   of    acid    it   will    save   calculation   and   the 
preparation  of  a  new  table,  if  the  acid  is  made  up  to  the  same  strength 


THE    ANALYSIS    OF    CEMENT     MIXTURES,     ETC. 


323 


as  before.  To  do  this  make  a  little  weaker  than  the  figures  call  for  and 
ascertain  its  strength  by  a  trial  determination  on  the  standard  sample, 
then,  if  too  much  carbonate  of  lime  is  found,  add  acid  cautiously  until 
the  value  of  a  determination  made  with  the  standard  sample  shows  the 
proper  percentage  of  lime. 

Standard  nitric  acid  may  be  used  in  place  of  the  standard  hydrochloric 
acid.  It  keeps  better  and  is  not  quite  so  volatile,  but,  on  the  other  hand, 
is  not  so  good  a  solvent.  On  the  cement-rock  mixtures  of  the  Lehigh 
District  hydrochloric  acid  works  best,  but  nitric  acid  is  used  in  the  lab- 
oratories of  several  wet  process  mills  in  the  west.  The  nitric  acid  is 


Fig.  107. — Automatic  pipette. 

prepared  exactly  as  the  hydrochloric  acid,  using  such  a  quantity  of 
strong  acid,  however,  as  will  contain  167  grams  of  HNOs. 

Fig.  106  shows  a  convenient  way  of  arranging  the  bottles,  burettes  and 
pipette  for  the  acid  and  alkali.  Its  construction  is  so  evident  from  the 
drawing  that  a  description  seems  unnecessary.  Both  the  burette  and 
pipette  are  of  the  Eimer  and  Amend  automatic  zero  pattern.  Fig.  107 
shows  the  pipette  in  detail. 

The  object  of  the  long  glass  tube  is  that  of  a  condenser  to  catch  any 
volatilized  acid.  This  may  be  replaced  by  a  Leibig's  return  condenser 


324 


PORTLAND  CEMENT 


cooled  by  water  or  by  a  tube  full  of  glass  beads,  which  are  wet  before 
the  determination  with  cold  distilled  water. 

A   water   cooled   condenser   which   is   used   in   the   laboratory   of   the 
Cowell   Portland    Cement   Co.,   Cowell,   Cal.,   is   shown   in   Fig.    108.    It 


Fig.  1 08.—  Condenser  for  acid  and  alkali  method. 

is  made  of  ordinary  iron  pipe.  The  condensers,  a,  a,  a,  a,  contain  each  a 
glass  tube,  b,  b,  b,  b,  held  in  place  by  rubber  stoppers.  Over  the  ends 
of  these  tubes  are  slipped  rubber  stoppers  which  fit  the  flasks,  c,  c,  c,  ct 
Water  enters  at  d,  and  flows  in  the  direction  of  the  arrows,  being  led 
from  one  condenser  to  the  next  through  the  side  pipes,  /,  /,  f,  and 
finally  out  at  c.  The  flow  of  water  is  controlled  by  the  valve,  d.  The 


THE    ANALYSIS    OF    CEMENT    MIXTURES,    ETC.  325 

glass  tube,  i,  is  attached  to  a  reservoir  of  distilled  water  and  the  tubes 
are  washed  into  the  flasks  by  means  of  the  small  jets,  h,  h,  h,  h.  This 
apparatus  will  be  found  very  convenient  where  many  determinations  are 
made.  If  the  flasks  show  a  tendency  to  slip  off  a  small  tin  collar  cut 
to  fit  half  way  around  the  neck  of  the  flask  as  shown  in  k,  and  attached 
to  the  tube  a  by  a  rubber  band  will  serve  to  keep  them  on. 

Mr.  F.  H.  Ronk,  Chemist,  Union  Portland  Cement  Co.,  in  a  communi- 
cation to  the  author  states  that  he  dispenses  with  the  long  glass  tube  and 
other  forms  of  condenser  entirely  and  obtains  just  as  good  results  by 
merely  boiling  the  sample  for  a  few  minutes  in  an  open  Erlenmeyer 
flask  on  the  hot-plate.  The  author  has  also  tried  this  method  and  found 
it  satisfactory. 

A  perpetual  table  for  use  with  any  strength  acid  and  alkali  may 
be  made  as  follows:  The  number  of  cubic  centimeters  and  twentieths 
cubic  centimeter  of  alkali  from  3  to  8  are  written  on  a  piece  of  stiff 
paper  and  pasted  fast  to  a  soft  pine  board.  The  percentages  and  tenths 
of  carbonate  of  lime  from  70  to  78  are  next  written  on  a  piece  of  card- 
board and  this  is  merely  fastened  to  the  board  with  thumb  tacks  so  that 
the  number  of  cubic  centimeters  of  acid  required  by  the  standard  sam- 
ple coincide  with  the  percentage  of  lime  it  contains.  For  instance,  in 
the  example  given  75  per  cent,  lime  are  made  to  coincide  with  4.6  cc.  of 
alkali.  The  board  is  then  to  be  hung  up  on  the  wall  behind  the  alkali 
burette,  etc. 

By  Measuring  the  Volume  of  CO ,  Evolved. 

At  one  time,  checks  upon  the  composition  were  made  to  some 
extent  in  this  country  by  means  of  calcimeters.  These  all  de- 
termine the  calcium  carbonate  indirectly  by  measuring  the  vol- 
ume of  carbon  dioxide  given  off.  These  calcimeters  are  still 
used  extensively  in  Europe  but  in  this  country  have  been  entirely 
superseded  by  the  simpler  and  fully  as  reliable  acid  and  alkali 
methods.  The  older  form  of  this  apparatus  was  that  of  Scheibler 
but  with  this  apparatus  tables  were  necessary  in  order  to  correct 
the  volume  of  gas  for  various  temperatures  and  pressures.  After 
Lunge  invented  the  compensating  tube  various  improved  calcim- 
eters were  devised  making  use  of  this  and  doing  away  with  the 
calculations  and  tables  required  by  the  Scheibler  apparatus.  It 
seems  probable,  however,  that  none  of  these  calcimeters  will  find 
extensive  use  in  this  country  and  most  German  chemists  who 
have  come  to  American  mills  have  discarded  them  for  the 
simpler  acid  and  alkali  method.  Those  who  are  interested  in 


326  PORTLAND  CEMENT 

this  method  of  determining  lime  are  referred  to  the  former  edi- 
tions of  this  book  for  a  description  of  Scheibler's  apparatus  and 
to  Butler's  "Portland  Cement"  and  Gatehouse's  "Handbook  for 
Cement  Work's  Chemists"  for  descriptions  of  other  improved 
forms  used  in  English  and  German  mills.  Marshall's  calcimeter 
is  described  in  Button's  Volumeric  Analysis,  and  is  also  in  Jour, 
is  described  in  Button's  Volumetric  Analysis,  and  also  in  Jour. 

By  Permanganate. 

Weigh  0.5  gram  of  the  sample  into  a  platinum  crucible  and  mix 
intimately,  by  stirring  with  a  glass  rod,  with  ^4  gram  of  finely 
powdered  dry  sodium  carbonate.  Brush  off  the  rod  into  the  cru- 
cible with  a  camel's-hair  brush.  Cover  the  crucible  and  place  over 
a  low  flame.  Gradually  raise  the  temperature  until  the  crucible  is 
red-hot.  Then  after  a  minute  or  two  remove  to  the  blast  lamp 
and  ignite  for  5  minutes.  Cool  the  crucible  by  plunging  its  bot- 
tom in  cold  water  and  place  in  a  400  cc.  beaker.  Cover  with  a 
watch-glass  and  add  40  cc.  of  (1-4)  hydrochloric  acid  (or  20  cc. 
of  water  and  20  cc.  of  hydrochloric  acid,  (i-i).  Heat  on  a  hot 
plate  until  solution  is  complete.  Lift  out  the  crucible  with  a  glass 
rod,  bent  in  a  crook  at  one  end,  and  rinse  it  off  into  the  beaker. 
Heat  the  contents  of  the  beaker  to  boiling,  add  ammonia  until 
alkaline,  and  then  10  cc.  of  a  ten  per  cent,  solution  of  oxalic  acid, 
and  proceed  as  directed  on  page  270. 

This  method  will  be  found  very  useful  in  checking  the  acid  and 
alkali  determinations. 

DETERMINATION  OF   SILICATES 

In  order  to  better  control  the  mixture  of  raw  materials  it  is 
often  of  advantage  to  determine  the  insoluble  matter  or  silicates. 
This  practice  differs  considerably  at  different  works,  but  the  fol- 
lowing will  illustrate  the  general  run  of  methods. 

By  Solution  and  Precipitation. 

Weigh  0.5  gram  of  the  sample  into  a  porcelain  dish  or  casserole, 
add  10  cc.  of  dilute  (i-i)  hydrochloric  acid  and  a  few  drops  of 
nitric  acid,  and  evaporate  to  dryness,  as  rapidly  as  possible,  with- 
out spattering.  Bake  at  about  120°  C.  until  all  odor  of  acid  has 


THE;  ANALYSIS  OF   CEMENT    MIXTURES,   ETC.  327 

disappeared  from  the  contents  of  the  dish.  Cool  the  latter,  add 
10  cc.  of  dilute  (i-i)  hydrochloric  acid  and  cover  with  a  watch- 
glass.  Heat  for  a  few  minutes  and  add  50  cc.  of  hot  water.  Boil 
a  few  minutes  and  add  ammonia  in  faint  excess.  Boil  a  little 
longer,  allow  to  settle  and  filter.  Wash  with  hot  water  a  few 
times,  ignite  and  weigh.  The  residue  is  called  "the  silicates"  and 
should,  provided  the  mix  is  of  proper  composition,  bear  a  certain 
ratio  to  the  percentage  of  carbonate  of  lime.  This  ratio  varies  at 
different  mills,  but  the  figure  is  usually  around  i :  3.6. 

By  Solution. 

Weigh  0.5  gram  of  the  mixture  into  a  beaker  and  boil  with  10 
per  cent,  hydrochloric  acid  for  five  minutes.  Filter  off  the  "in- 
soluble matter,"  wash,  ignite  and  weigh.  This  method  is  in  use  in 
the  laboratories  of  the  Sandusky  Portland  Cement  Co.,  and  the 
mix  is  so  proportioned  as  to  give  a  certain  ratio  between  this  "in- 
soluble matter"  and  the  lime.  This  ratio  varies  at  the  two  mills 
of  the  company.  At  the  Sandusky  mill  the  ratio  is  3.9  and  at  the 
Syracuse  mill  it  is  4.2,  the  higher  ratio  being  due  to  the  more 
silicious  clay  at  the  latter  point. 

COMPLETE  ANALYSIS  OF  CEMENT  MIXTURE 
OR  SLURRY. 

Method  of  the  Committee  on  Uniformity  in  Analysis  of  Materials 
for  the  Portland  Cement  Industry  of  the  New  York  Sec- 
tion of  the  Society  of*  Chemical  Industry. 

One-half  gram  of  the  finely  powdered  substance  is  weighed  out 
and  strongly  ignited  for  15  minutes,  or  longer  if  the  blast  is  not 
powerful  enough  to  effect  complete  conversion  to  cement  in  this 
time.  It  is  then  transferred  to  an  evaporating  dish,  preferably 
of  platinum  for  the  sake  of  celerity  in  evaporation,  and  the 
analysis  completed  as  directed  on  page  253  by  moistening  with 
water  and  digesting  with  hydrochloric  acid,  etc. 

The  above  method  is  tedious  and  so  cumbersome  and  long  as 
to  preclude  its  use  in  cement  mill  laboratories,  where  samples  of 
the  mix  are  analyzed  daily,  except  for  the  preparation  of  standard 
samples.  Even  these  should  be  analyzed  also  by  the  method  in 


328  PORTLAND  CEMENT 

daily  use  in  the  laboratory  in  order  to  get  all  the  work  on  the 
same  relative  basis  and  the  longer  and  more  accurate  results 
should  only  be  used  to  check  the  shorter  mill  scheme,  and  to  make 
sure  that  the  results  of  the  latter  are  not  too  wide  of  the  truth. 
The  results  which  should  actually  be  used  as  the  values  for  the 
carbonate  of  lime,  etc.,  in  the  samples  should  be  those  obtained 
by  the  regular  mill  scheme.  If  this  is  not  done,  acid  and  alkali 
will  give  one  set  of  results  and  a  complete  analyses  another,  etc. 
The  scheme  given  below  is  modeled  after  those  generally  in 
use  in  cement  mill  laboratories  and  combines  a  fair  degree  of  ac- 
curacy with  rapidity  and  convenience  of  execution. 

Method  of  the  Committee  on  the  Analysis  of  Portland  Cement 
and  Cement  Materials  of  the  Lehigh  Valley  Section  of  the 

American  Chemical  Society. 

Weigh  0.5  gram  of  the  finely  ground  sample  into  a  small  plati- 
num crucible  and  mix  intimately,  by  stirring  with  a  glass  rod, 
with  0.5  gram  of  pure  dry  finely  powdered  sodium  carbonate. 
Brush  off  the  rod  into  the  crucible  with  a  camel's-hair  brush. 
Cover  the  crucible  and  place  over  a  low  flame.  Gradually  raise 
the  latter,  until  the  crucible  is  red-hot,  and  continue  heating,  in 
the  full  flame  of  the  Bunsen  burner,  for  five  minutes  longer ;  then 
place  over  a  blast  lamp  and  heat  for  five  minutes  more.  Cool  and 
place  the  crucible  on  its  side  in  a  porcelain  casserole  or  dish,  or 
preferably  a  platinum  dish,  and  dissolve  the  mass  in  10  cc.  of 
water  and  10  cc.  of  hydrochloric  acid.  Heat  until  solution  is 
complete,  keeping  the  dish  covered  to  avoid  loss  by  effervescence. 
When  everything,  except  a  little  gelatinous  silica,  which  usually 
separates  out,  is  in  solution,  remove  the  crucible  and  clean  off 
into  the  dish  with  a  rubber-tipped  rod.  Evaporate  to  dryness  at 
a  moderate  heat,  continuing  to  heat  the  mass — not  above  200°  C. 
— until  all  odor  of  acid  is  gone.  Do  not  hurry  this  baking  or 
skimp  the  time.  The  whole  success  of  the  analysis  depends  on 
thoroughness  at  this  point.  Cool;  add  20  cc.  hydrochloric  acid 
(i-i)  ;  cover,  and  boil  gently  for  ten  minutes;  add  30  cc.  water, 
raise  to  boiling,  and  filter  off  the  silica ;  wash  with  hot  water  four 
or  five  times:  out  in  crucible,  ignite  (using  blast  for  10  minutes  V 
and  weigh  as  SiO2. 


THE    ANALYSIS    OF    CEMENT     MIXTURES,     ETC.  329 

Iron  and  Alumina. 

Make  filtrate  alkaline  with  ammonia,  taking  care  to  add  only 
slight  excess ;  add  a  few  drops  of  bromine  water  and  boil  till  odor 
of  ammonia  is  faint.  Filter  off  the  hydroxides  of  iron  and  alum- 
inum, washing  once  on  the  filter.  Dissolve  the  precipitate  with 
hot  dilute  nitric  acid,  precipitate  with  ammonia;  boil  five  min- 
utes ;  filter  and  wash  the  iron  and  alumina  with  hot  water  once ; 
place  in  crucible,  ignite  carefully,  using  blast  for  5  minutes,  and 
weigh  combined  iron  and  aluminum  oxides. 

Iron. 

If  it  is  desired  to  separate  the  two  oxides  add  four  grams  acid 
potassium  sulphate  to  the  crucible  and  fuse  at  a  very  low  heat 
until  oxides  are  wholly  dissolved — twenty  minutes  at  least ;  cool ; 
place  crucible  and  cover  in  small  beaker  with  50  cc.  water;  add 
15  cc.  dilute  sulphuric  acid  (1-4)  ;  cover  and  digest  at  nearly  boil- 
ing until  melt  is  dissolved;  remove  crucible  and  cover  rinsing 
them  carefully.  Cool  the  solution  and  add  10  grams  powdered  C. 
P.  zinc,  No.  20.  Let  stand  one  hour,  decant  the  liquid  into  a 
larger  beaker,  washing  the  zinc  twice  by  decantation,  and  titrate 
at  once  with  permanganate.  Calculate  the  Fe2O3  and  determine 
the  A12O3  by  difference.  Test  Zn,  etc.,  by  a  blank  and  deduct. 

Iron  may  also  be  determined  by  using  a  separate  sample,  ignit- 
ing with  half  its  weight  sodium  carbonate,  dissolving  the  mass 
in  hydrochloric  acid  and  titrating  with  stannous  chloride  as 
directed  on  page  277  or  the  iron  may  be  precipitated  with 
ammonia  redissolved  in  sulphuric  acid,  and  the  iron  determined 
by  reduction  with  zinc  and  titration  with  permanganate.  (See 
page  271). 

Lime. 

Make  the  filtrate  from  the  hydroxides  alkaline  with  ammonia; 
boil;  add  20  cc.  boiling  saturated  solution  ammonium  oxalate; 
continue  boiling  for  five  minutes;  let  settle  and  filter.  Wash  the 
calcium  oxalate  thoroughly  with  hot  water,  using  not  more  than 
125  cc.,  and  transfer  it  to  the  beaker  in  which  it  was  precipitated, 
spreading  the  paper  against  the  side  and  washing  down  the  pre- 
cipitate first  with  hot  water  and  then  with  dilute  sulphuric  acid 


330  PORTLAND  CEMENT 

(1-4);  remove  paper;  add  50  cc.  water,  10  cc.  Cone,  sulphuric 
acid,  heat  to  incipient  boiling  and  titrate  with  permanganate,  cal- 
culating the  CaO. 

Magnesia. 

If  the  filtrate  from  the  calcium  oxalate  exceeds  250  cc. ;  acidify, 
evaporate  to  that  volume;  cool,  and  when  cold  add  15  cc.  strong- 
ammonia  and  with  stirring  15  cc.  stock  solution  of  sodium  hy- 
drophosphate.  Allow  to  stand  in  the  cold  six  hours  or  preferably 
over  night ;  filter ;  wash  the  magnesium  phosphate  with  dilute  am- 
monia (1-4)  plus  100  gms.  ammonium  nitrate  per  liter;  put  in 
crucible,  ignite  at  low  heat  and  weigh  the  magnesium  pyrophos- 
phate. 

Other  Constituents. 

For  the  determination  of  sulphur,  carbon  dioxide,  hygroscopic 
and  combined  water,  and  alkalies,  refer  to  the  methods  given 
under  cement.  The  fusion  method  is  to  be  used  for  determining 
sulphur  which  is  usually  present  as  sulphide  (iron  pyrites)  or  in 
combination  with  organic  matter  in  mixtures  of  marl  and  clay. 
Calcium  sulphate  may  be  determined  by  simple  solution  in  hydro- 
chloric acid  as  in  cement. 


Chapter  XII. 


THE  ANALYSIS  OF  THE  RAW  MATERIALS. 


METHODS  FOR  LIMESTONE,  CEMENT-ROCK  AND  MARL. 
By  Ignition  of  the  Sample  with  Sodium  Carbonate. 

Silica. 

Weigh  0.5  gram  of  finely  ground  dried  sample  into  a  platinum 
crucible  and  mix  intimately  with  0.5  gram  of  pure  dry  sodium 
carbonate  by  stirring  with  a  glass  rod.  Place  the  crucible  over 
a  low  flame  and  gradually  raise  this  latter  until  the  crucible  is  red- 
hot.  Continue  heating  for  five  minutes,  then  substitute  a  blast 
lamp  for  the  Bunsen  burner  and  heat  for  five  minutes  longer. 
Place  the  crucible  in  a  dish  or  casserole,  add  40  cc.  of  water  and 
ib  cc.  of  hydrochloric  acid,  and  digest  until  all  the  mass  is  dis- 
solved out  of  the  crucible.  Clean  off  the  crucible  inside  and  out- 
side, add  a  few  drops  of  nitric  acid  to  the  solution  and  evaporate 
it  to  dryness.  Heat  the  residue  at  no0  C.  for  one  hour,  cool,  add 
15  cc.  of  dilute  hydrochloric  acid,  cover  with  a  watch-glass  and 
digest  for  a  few  minutes  on  a  hot-plate.  Dilute  with  50  cc.  of 
hot  water,  heat  nearly  to  boiling,  and  filter.  Wash  the  residue 
well  with  hot  water.  Dry,  ignite,  and  weigh  as  silica,  SiO2. 

If  the  limestone  is  high  in  silica  a  trace  will  be  found  in  the  fil- 
trate from  the  silica  as  precipitated  above.  If  great  accuracy  is 
desired,  after  evaporation  to  dryness,  dissolve  the  mass  in  the 
dish  in  hydrochloric  acid  and  water  as  usual  without  heating  it  to 
1 10°  C.  for  one  hour  and  filter  and  wash.  Evaporate  the  filtrate 
to  dryness,  and  again  dissolve  in  water  and  hydrochloric  acid,  fil- 
ter, and  wash.  Ignite  the  two  precipitates  together  and  weigh  as 
SiCX. 

Ferric  O.vidc  and  Alumina. 

Heat  the  filtrate  to  boiling,  add  ammonia  in  slight  but  distinct 
excess,  boil  for  five  minutes  and  filter.  Wash  the  precipitate  twice 


332  PORTLAND  CEMENT 

with  hot  water.  Remove  the  filtrate  from  under  the  funnel  and 
in  its  place  stand  the  beaker  in  which  the  precipitation  was  made. 
Dissolve  the  precipitate  in  dilute  nitric  acid  and  wash  the  filter- 
paper  free  from  iron  with  cold  water.  Heat  the  solution  to  boil- 
ing and  precipitate  the  iron  and  alumina  with  ammonia  as  before. 
Filter,  allowing  the  filtrate  to  run  into  that  from  the  first  precipita- 
tion, wash  once  with  hot  water,  dry  and  ignite.  Weigh  and  re- 
port as  ferric  oxide  and  alumina. 

If  the  percentage  of  ferric  oxide  and  alumina  are  desired  sepa- 
rately, proceed  as  directed  in  A,  B,  C,  or  D. 

A.  Ignite  one  gram  of  the  sample  with  one-half  gram  of 
sodium  carbonate  as  directed  under  silica.    Dissolve  the  sintered 
mass  in  dilute  hydrochloric  acid.     Heat  to  boiling,  reduce  with 
stannous  chloride  and  titrate  with  standard  bichromate  -as  di- 
rected on  page  277. 

B.  Fuse  the  precipitate  of  ferric  oxide   and   alumina,   after 
weighing,  with  a  little  sodium  carbonate,  dissolve  in  a  little  water 
to  which  a  few  cubic  centimeters  of  hydrochloric  acid  have  been 
added,  and  drop  into  the  solution  a  few  small  crystals  of  citric 
acid.    Add  ammonia  until  the  solution  smells  slightly  of  the  re- 
agent, and  then  an  excess  of  ammonium  sulphide.     Allow  the 
black  precipitate  to  settle,  filter,  wash  a  few  times,  dissolve  in  hy- 
drochloric acid,  add  a  little  bromine  water,  boil  a  while  and  add 
ammonia  in  slight  but  distinct  excess.    Filter,  wash  well  with  hot 
water,  ignite  and  weigh  as  Fe2O3.    Deduct  this  weight  from  that 
of  the  total  ferric  oxide  and  alumina,  for  the  weight  of  alumina, 
A1203. 

C.  Fuse  the  precipitate  of   ferric  oxide  and  alumina,   after 
weighing,  with  caustic  potash  in  a  silver  crucible  or  dish.     Treat 
the  fusion  with  water,  boil,  filter,  and  wash.     Dry,  ignite,  and 
weigh  the  residue  as  ferric  oxide,  Fe2O3.     Deduct  this  weight 
from  that  of  the  ferric  oxide  and  alumina,  for  the  weight  of 
alumina,  A12O3. 

D.  Dissolve  the  residue,  after  fusion  with  sodium  carbonate,  in 
a  little  dilute  hydrochloric  acid  and  determine  the  ferric  oxide 
volumetrically  by  the  method  given  on  page  277. 


THE    ANALYSIS    OF    THE    RAW    MATERIALS  333 

Lime. 

Heat  the  filtrate  from  the  iron  and  alumina,  which  should  meas- 
ure between  300  and  500  cc.,  to  boiling  and  add  25  cc.  of  a  sat- 
urated solution  of  ammonium  oxalate.  Stir  and  boil  for  a  few 
minutes  and  allow  the  precipitate  one  hour  in  which  to  settle. 
Filter  and  wash  well  with  hot  water.  After  washing,  treat  the 
precipitate  as  directed  below  in  A  or  B. 

A.  Punch  a  hole  in  the  filter-paper  and  wash  the  precipitate  into 
the  beaker  in  which  the  precipitation  was  formed.     Wash  the 
paper  with  dilute  sulphuric  acid  from  a  wash-bottle  and  then  with 
hot  water.     Dilute  the  solution  to  300  or  40  cc.,  heat  to  60°  or 
70°  C.,  and  after  adding  10  cc.  of  dilute  sulphuric  acid  titrate  with 
permanganate.    Calculate  the  per  cent,  of  lime,  CaO,  or  calcium 
carbonate,  CaCO3,  in  the  limestone,  as  directed  under  "Volu- 
metric Determination  of  Calcium,"  page  266. 

B.  Dry  the  precipitate  by  heating  over  a  low  flame,  in  weigh- 
ed platinum  crucible,  ignite  until  all  carbonaceous  matter  is  de- 
stroyed and  ignite  for  fifteen  minutes  over  a  blast  lamp.    Cool  and 
weigh.     Again  ignite  for  five  minutes  over  a  blast  lamp  and 
weigh.    If  this  weight  agrees  to  within  0.0002  gram  of  the  former 
one  it  may  be  taken  as  the  weight  of  the  calcium  oxide,  CaO. 
If  it  does  not  agree,  ignite  again  and  repeat,  if  necessary,  until 
the  weight  is  constant. 

Magnesia. 

To  the  filtrate  from  the  calcium  oxalate  add  sufficient  hydro- 
chloric acid  to  make  it  slightly  acid,  and  30  cc.  of  sodium  phos- 
phate solution.  Concentrate  to  about  200  cc.  by  evaporation.  Set 
the  solution  in  a  vessel  of  cold  water  and  when  cooled  to  the  tem- 
perature of  the  latter  add  ammonia,  drop  by  drop,  from  a  burette, 
with  constant  stirring  until  slightly  ammoniacal  and  the  precipi- 
tate begins  to  form.  Stop  adding  ammonia  and  stir  for  five  min- 
utes, add  one-tenth  the  volume  of  the  liquid  of  strong  ammonia 
and  continue  the  stirring  for  three  minutes  more.  Allow  the  solu- 
tion to  stand  in  a  cool  place  over  night,  filter,  wash"  well  with  a 
mixture  of  1000  cc.  water,  500  cc.  ammonia  (sp.  gr.  0.96),  and 
150  grams  ammonium  nitrate.  Dry,  ignite,  and  weigh  as  mag- 


334  PORTLAND  CEMKNT 

nesium  pyrophosphate,  Mg2P;,OT.  Multiply  tliis  by  0.36219  for 
its  equivalent  of  magnesia,  MgO,  or  by  0.75744  for  magnesium 
carbonate,  MgCOy. 

By  Solution  in  Hydrochloric  Acid. 

Insoluble   Silicious   Matter. 

Weigh  0.5  gram  of  the  finely  ground  dried  sample  into  a  porcelain 
dish  or  casserole,  cover  with  a  watch-glass  and  add  30  cc.  of  water  and 
10  cc.  of  concentrated  hydrochloric  acid.  Warm  until  all  effervescence 
has  ceased,  uncover,  add  a  few  drops  of  nitric  acid,  and  evaporate  to 
dryness.  Bake  on  the  hot-plate  or  sand-bath  until  all  odor  of  hydro- 
chloric acid  has  disappeared,  or  safer  still,  heat  in  an  air-bath  at  110° 
C.  for  one  hour  after  the  residue  has  become  perfectly  dry.  Cool  the 
dish  and  add  5  cc.  of  dilute  hydrochloric  acid,  set  on  the  hot-plate, 
covered  with  a  watch-glass  for  five  minutes,  then  add  50  cc.  of  hot  water 
and  filter,  after  digesting  until  all  except  silicious  matter  dissolves. 
Wash  thoroughly,  ignite  and  weigh  as  "insoluble  silicious  matter." 

Silica. 

Should  it  be  desirous  to  know  the  silica  in  the  "insoluble  silicious 
matter"  fuse  it  with  ten  times  its  weight  of  pure  dry  sodium  carbonate, 
first  over  a  Bunsen  burner  turned  low,  and  then,  after  slowly  raising 
the  flame  of  this  latter  to  its  full  height,  over  a  blast  lamp  until  the 
contents  of  the  crucible  are  in  a  state  of  quiet  fusion.  Remove  the 
crucible  from  the  lamp  and  run  the  fused  mass  well  up. on  its  sides  by 
tilting  and  revolving  the  crucible  while  held  with  the  crucible  tongs. 
While  still  hot  dip  the  crucible  three-quarters  of  the  way  up  in  a  pan 
of  cold  water  which  will  frequently  cause  the  mass  to  loosen  from  the 
crucible.  Wash  off  any  material  spattered  on  the  crucible  cover  into  a 
casserole  or  dish  with  hot  water,  and  add  the  mass  in  the  crucible  if  it 
has  become  detached.  If  not,  fill  the  crucible  with  hot  water  and  set  on 
the  hot-plate  until  the  fused  mass  softens  and  can  be  removed  to  the 
casserole.  Dissolve  any  particles  of  the  mass  in  hydrochloric  acid, 
that  adhere  too  firmly  to  the  crucible  to  be  removed  by  gentle  rubbing 
with  a  rubber-tipped  rod.  When  the  hot  water  has  thoroughly  disin- 
tegrated the  fused  mass,  cover  the  casserole  or  dish  with  a  watch-glass 
and  strongly  acidify  the  contents  with  hydrochloric  acid.  Heat  until 
all  effervescence  ceases  and  everything  dissolves  except  the  silica.  Wash 
off  the  watch-glass  into  the  dish  and  evaporate  the  solution  to  dryness. 
Heat  for  one  hour  at  110°  C.  in  the  air-bath,  or  on  the  hot-plate  at  not 
too  high  a  temperature  until  all  odor  of  hydrochloric  acid  has  disap- 
peared from  the  dry  mass.  Cool,  add  10  cc.  of  hydrochloric  acid  and  50 
cc.  of  water,  warm  until  all  soluble  salts  are  in  solution,  filter,  wash  well 
with  hot  water,  dry,  ignite,  and  weigh  as  silica,  SiO2. 


THE    ANALYSIS    OF    THE    RAW    MATERIALS  335 


Mix  the  two  filtrates  from  the  silica  separations  and  proceed  to  de- 
termine iron  and  alumina,  lime  and  magnesia,  as  directed  in  the  method 
"By  Ignition  with  Sodium  Carbonate." 

When  the  amount  of  sodium  carbonate  added  to  the  "insoluble  silic- 
ious  matter'5  is  greater  than  0.5  gram,  it  is  best  in  very  accurate  work, 
instead  of  mixing  the  two  filtrates  from  the  silica,  to  determine  the 
iron,  alumina,  lime,  and  magnesia  in  each  solution  separately,  since  the 
large  line  precipitate  is  almost  sure  to  be  contaminated  with  sodium 
salts  if  the  two  filtrates  are  mixed. 

Determination    of    Organic    Matter,    Insoluble    Silicious    Matter,    Ferric 
Oxide  and  Alumina,  Lime  and  Magnesia. 

Weigh  i  gram  of  the  finely  ground  dried  limestone  into  a  porcelain 
dish  or  casserole;  cover  with  a  watch-glass  and  add  30  cc.  of  water  and 
10  cc.  of  concentrated  hydrochloric  acid.  Warm  until  all  effervescence 
ceases,  uncover  and  evaporate  to  dryness  on  a  water-bath.  Heat  the 
dish  for  one  hour,  after  the  residue  becomes  thoroughly  dry,  at  no0 
C.  in  an  air-bath.  Cool  the  dish  and  add  5  cc.  of  hydrochloric  acid 
50  cc.  of  hot  water.  Heat  until  all  soluble  salts  dissolve,  filter  upon 
a  Gooch  crucible  or  a  small  counterpoised  filter-paper.  Wash  well  with 
hot  water,  dry  at  100°  C.  in  an  air-bath  and  weigh  as  "organic  matter" 
plus  "insoluble  silicious  matter." 

Now  ignite  until  all  carbonaceous  matter  is  destroyed,  and  cool  and 
weigh  as  "insoluble  silicious  matter."  This  weight  subtracted  from  the 
preceding  one  gives  the  "organic  matter."  If  the  silica  in  the  "in- 
soluble silicious  matter"  is  desired,  fuse  the  latter  with  ten  times  its 
weight  of  sodium  carbonate  and  proceed  as  described  in  the  preceding 
scheme  for  the  analysis  of  limestone  "By  Solution  in  Hydrochloric  Acid." 

Heat  the  filtrate  from  the  "organic  matter"  and  the  "insoluble  silic- 
ious matter"  to  boiling,  add  ammonia  in  slight  but  distinct  excess,  and 
proceed  to  determine  the  ferric  oxide  and  alumina,  lime  and  magnesia, 
as  directed  on  page  331. 

The  Determination  of  Alkalies,  Sulphuric  Acid,  Carbon  Dioxide 
Combined  Water  and  Loss  on  Ignition. 

For  the  determination  of  these  constituents  refer  to  the  meth- 
ods given  under  cement.  Use  the  fusion  method  for  sulphur  and 
employ  only  l/2  gram  for  a  sample  in  determining  carbon  dioxide. 

Rapid  Determination  of  Lime  and  Magnesia. 

S.  B.  Newberry1  suggests  the  following  rapid  scheme  for  de- 

Cement  and  Engineering  News,  March,  1903,  p.  35. 


336  PORTLAND  CEMENT 

termining  lime  and  magnesia  in  limestone,  etc.  "Prepare  one- 
fifth  normal  hydrochloric  acid  and  one-fifth  normal  caustic  soda 
solutions,  and  standardize  with  pure,  transparent  Iceland  spar. 
One-half  gram  of  spar  should  exactly  neutralize  50  cc.  of  acid. 

Weigh  out  one-half  gram  of  finely-ground  limestone,  transfer 
to  an  Erlenmeyer  flask  of  about  500  cc.  capacity,  provided  with 
rubber  stopper  and  thin  glass  tube  about  30  inches  long  to  serve 
as  a  condenser,  as  described  on  page  236.  Run  into  the  flask  60 
cc.  one-fifth  normal  acid ;  attach  the  condenser  and  boil  gently,  al- 
lowing no  steam  to  escape  from  the  tube,  for  about  two  minutes. 
Wash  down  the  tube  into  the  flask  with  a  few  cc.  of  water  from 
wash-bottle;  remove  the  condenser  and  cool  the  solution  thor- 
oughly by  immersing  the  bottom  of  the  flask  in  cold  water.  When 
quite  cold,  add  five  drops  of  phenolphthalein  solution,  ( I  gm.  in 
200  cc.  alcohol),  and  titrate  back  to  first  pink  color  with  one-fifth 
normal  soda  solution.  It  is  important  to  recognize  the  point  at 
which  a  faint  pink  color  first  appears  throughout  the  solution, 
even  though  this  may  fade  out  in  a  few  seconds.  If  alkali  be  add- 
ed to  a  permanent  and  strong  red  color,  the  lime  will  come  too 
low.  Let  us  call  the  amount  of  acid  used  the  first  acid,  and  the 
alkali  used  to  titrate  back  the  first  alkali. 

"Transfer  the  neutral  solution  to  a  large  test-tube,  twelve 
inches  long  and  one  inch  inside  diameter,  marked  (with  a  paper 
strip  or  otherwise)  at  100  cc.  Heat  to  boiling,  and  add  one-fifth 
normal  soda  solution,  about  one  cc.  at  a  time,  boiling  for  a  mo- 
ment after  each  addition,  till  a  deep  red  color,  which  does  not  be- 
come paler  on  boiling,  is  obtained.  This  point  can  be  easily  rec- 
ognized within  one-half  cc.  after  a  little  practice.  Note  the 
number  of  cc.  soda  solution  added  to  the  neutral  solution,  as 
second  alkali.  Dilute  to  100  cc.,  boil  for  a  moment  and  set  the 
tube  aside  to  allow  the  precipitate  to  settle.  When  settled,  take 
out  50  cc.  of  the  clear  solution  by  means  of  a  pipette,  and  titrate! 
back  to  colorless  with  one-fifth  normal  acid.  Multiply  by  2  the 
number  of  cc.  acid  required  to  neutralize,  and  not  as  second  acid. 

"The  calculation  is  as  follows: 


THE    ANALYSIS    OF    THE    RAW    MATERIALS  337 

Second  alkali  —  second  acid,  X  2  X  0.40  —  %.  MgO. 

First  acid  —  (first  alkali  -f-  second  alkali  —  second  acid), 
X  2  X  0.56  =  %  CaO. 

"Example:  To  one-half  gram  limestone  were  added  60.00  cc. 
acid,  (first  acid).  To  titrate  back  to  first  pink,  11.60  cc.  alkali 
were  required,  (first  alkali).  The  solution  was  then  transferred 
to  test-tube,  boiled,  and  3.55  alkali  added  to  permanent  deep 
red  color,  (second  alkali).  After  diluting  to  100  cc.  and  settling, 
50  cc.  of  the  red  solution  required  0.45  cc.  acid  to  decolorize  it, 
(0.45  X  2  =  0.90  =  second  acid). 

3-55— °-9°»  X  2  X  0.40  =  2.12%  MgO. 

60.00—  (11.60  +  3-55—0-90)  X  2  X  0.56  =  51.24%  CaO." 

NOTES. 

"Nitric  acid  may  be  used  in  place  of  hydrochloric;  the  latter  appears, 
however,  to  give  slightly  better  results. 

"Not  more  than  i  cc.  excess  of  alkali  should  be  added  in  precipitating 
the/  magnesia;  the  'second'  should  therefore  not  exceed  i.o.  Larger 
excess  of  alkali  tends  to  throw  down  lime. 

"The  settling  usually  requires  only  a  few  minutes,  unless  much  mag- 
nesia is  present;  it  may  be  greatly  hastened  by  allowing  the  test-tube  to 
stand  two  or  three  minutes,  then  immersing  the  lower  part  for  a  moment 
in  cold  water. 

"If  results  are  desired  in  percentages  of  magnesium  carbonate  and 
calcium  carbonate  the  factors  0.84  and  i.oo  are  to  be  substituted  for  0.40 
and  0.56,  respectively. 

"The  tendency  of  the  method  is  to  give  slightly  too  high  results  on 
magnesia  and  too  low  results  on  lime.  This  is  partly  due  to  the  forma- 
tion of  calcium  carbonate,  by  the  action  of  the  carbon  dioxide  of  the 
air,  during  the  precipitation  of  the  magnesia.  By  the  use  of  a  large 
test-tube,  as  above  described,  this  error  is  so  far  reduced  as  to  be 
insignificant.  Another  source  of  shortage  of  lime  is  to  be  found  in  the 
presence,  in  certain  materials,  of  small  proportions  of  lime  in  a  form 
insoluble  in  dilute  acid." 

In  determining  lime  in  cement-rock  or  in  cement  mixtures  made  from 
clay  containing  calcium  silicates  this  method  always  gives  low  results 
for  the  above  reason.  To  use  the  method  on  such  material  it  is  necessary 
to  determine  a  "correction  factor"  by  comparison  between  the  lime 
found  by  this  method  and  that  on  page  256,  in  a  series  of  standard 
samples.  By  subtracting  the  lower  from  the  higher  results,  a  constant 
is  obtained  which  is  to  be  added  to  all  results  obtained  by  titration  with 
the  acid  and  alkali. 
22 


338  PORTLAND  C£M£NT 

METHODS  FOR  CLAY. 

Silica. 

Finely  grind  the  sample  of  clay  and  heat  at  100°  to  110°  C.  for 
one  hour  in  an  air-bath.  Transfer  I  gram  of  the  dried  clay  to  a 
fairly  large  platinum  crucible.  Mix  with  it  by  stirring  with  a 
smooth  glass  rod  10  grams  of  sodium  carbonate  and  a  little  so- 
dium nitrate.  Heat  over  a  Bunsen  burner,  gently  at  first,  for  a 
few  minutes  and  then  to  quiet  fusion  over  a  blast  lamp.  Run  the 
fused  mass  well  up  on  the  sides  of  the  crucible  and  allow  to  cool. 
Nearly  fill  the  crucible  with  hot  water  and  set  on  the  hot-plate  for 
a  few  minutes.  Pour  the  solution  and  as  much  of  the  mass  as  has 
become  detached  from  the  crucible  into  a  casserole  or  better  a 
platinum  dish.  Repeat  this  treatment  until  the  mass  has  become 
thoroughly  disintegrated.  Treat  what  remains  in  the  crucible 
with  dilute  hydrochloric  acid  and  pour  the  acid  into  the  casserole 
or  dish.  Clean  out  the  crucible  with  a  rubber-tipped  rod  and  after 
acidifying  with  hydrochloric  acid  evaporate  the  contents  of  the 
casserole  to  dryness.  Proceed  as  in  A  or  B. 

A.  Heat  in  an  air-bath  at  110°  C.  for  one  hour,  or  until  all  odor 
of  hydrochloric  acid  has  vanished.     Cool,  moisten  the  mass  with 
dilute  hydrochloric  acid,  add  a  little  water  and  again  evaporate 
to  dryness.    Now  add  30  cc.  of  dilute  hydrochloric  acid,  digest  at 
a  gentle  heat  for  a  few  moments  and  add  100  to  150  cc.  of  hot 
water,  Allow  to  stand  a  few  minutes  on  the  hot-plate  and  filter. 
Wash  the  residue  thoroughly  with  hot  water,  ignite  over  a  Bun- 
sen  burner  until  all  carbon  is  burned  off,  and  then  for  five  min- 
utes over  a  blast  lamp,  and  weigh  as  SiO2. 

B.  The  residue,  without  further  heating,  is  treated  at  first  with 
10  cc.  of  dilute  HC1.    The  dish  is  then  covered  and  digestion  al- 
lowed to  go  on  for  10  minutes  on  the  bath,  after  which  the  solu- 
tion is  diluted  slightly,  filtered,  and  the  separated  silica  washed 
thoroughly  with  hot  water.     The  filtrate  is  again  evaporated  to 
dryness,  the  residue,  without  further  heating,  taken  up  with  acid 
and  water,  and  the  small  amount  of  silica  it  contains  separated  on 
another  filter-paper.     The  two  papers  containing  the  residue  are 
transferred  wet  to  a  weighed  platinum  crucible,  dried,  ignited, 


THE  ANALYSIS  OF  THE  RAW  MATERIALS  339 

first  over  a  Bunsen  burner  until  the  carbon  of  the  filter  is  com- 
pletely consumed,  and  finally  over  the  blast  for  15  minutes.  The 
precipitate  is  then  weighed  as  SiO2.  This  precipitate  is  more  or 
less  contaminated  by  iron  oxide  and  alumina.  In  accurate  work 
the  amount  of  these  must  be  determined  in  the  following  manner 
and  deducted  from  the  weight  of  SiO2  as  found  above.  Moisten 
the  weighed  silica  with  a  few  drops  of  dilute  sulphuric  acid  and 
half  fill  the  crucible  with  hydrofluoric  acid.  Evaporate  to  dryness 
by  placing  over  a  burner  in  an  inclined  position  so  that  the  low 
flame  plays  upon  the  side  of  the  crucible  and  the  evaporation  takes 
place  only  from  the  surface.  Ignite  and  weigh.  The  difference 
between  the  two  weights  is  the  silica,  SiO2. 

Ferric  Oxide  and  Alumina. 

Add  a  few  drops  of  bromine  water  and  heat  the  filtrate  from 
the  silica,  which  should  measure  about  150  cc.,  to  boiling,  and 
add  ammonia  in  slight  but  distinct  excess ;  boil  for  a  few  moments 
and  allow  the  precipitate  to  settle.  Filter  and  wash  several  times 
with  hot  water.  Remove  the  filtrate  from  under  the  funnel  and 
dissolve  the  precipitate  of  iron  and  alumina  in  a  mixture  of  15  cc. 
of  dilute  nitric  acid  and  15  cc.  of  cold  water,  by  pouring  back 
and  forth  through  the  filter  as  long  as  any  precipitate  remains. 
Wash  the  filter-paper  well  with  cold  water,  dry,  place  in  the 
weighed  platinum  crucible  containing  the  residue  from  the  puri- 
fication of  the  silica  if  this  has  been  done,  and  set  aside.  Repre- 
cipitate  the  iron  and  alumina  in  the  filtrate  as  before  by  adding  a 
slight  but  distinct  excess  of  ammonia,  filter,  and  wash  once  with 
hot  water.  Place  in  the  crucible  with  the  other  paper  and  ignite, 
using  the  blast  as  in  determining  silica  and  weigh  as 
Fe2O3  +  ALA(TiO2  +  P2O5  +  Mn3O4). 

Determine  the  ferric  oxide  in  the  precipitate  as  in  A,  B  or  C 
below  and  subtract  the  amount  from  this  weight;  the  difference 
will  be  the  Al2O3(TiO2  +  P2O5  +  Mn3O4). 

A.  Fuse  the  ignited  precipitate  with  sodium  carbonate,  treat  the 
fused  mass  with  hot  water  and  wash  it  out  into  a  small  beaker, 
allow  the  residue  to  settle  and  decant  off  the  clear  supernatant 
liquid  through  a  small  filter,  leaving  the  residue  in  the  bottom  of 


340  PORTLAND 

the  beaker.  Wash  the  filter-paper  once  and  pour  a  little  hot  con- 
centrated hydrochloric  acid  through  the  filter  into  the  beaker  con- 
taining the  residue.  Heat  gently,  but  do  not  boil.  When  all  the 
residue  is  dissolved,  determine  the  iron  in  the  solution  by  re- 
duction with  stannic  chloride  and  titration  with  potassium  bichro- 
mate as  directed  on  page  277. 

B.  The  precipitate  is  fused  with  3  or  4  grams  of  potassium  bi- 
sulphate  at  a  very  low  temperature  and  the  melt  is  dissolved  in 
water  acidified  with  sulphuric  acid.    The  solution  is  then  reduced 
with  zinc  or  hydrogen  sulphide,  (preferably  the  latter  since  clays 
sometimes  contain  considerable  titanic  oxide),  and  the  iron  deter- 
mined as  directed  on  page  271. 

C.  Weigh  out  a  fresh  sample  of  j£   gram.     Mix  intimately 
with  2  grams  of  precipitated  calcium  carbonate  and  2  grams  of 
sodium  carbonate.     Ignite  for   15  minutes  in  a  large  platinum 
crucible  over  a  good  blast  lamp.     Cool  the  mass  and  dissolve  in 
dilute  hydrochloric  acid.     If  much  silica  separates  out  evaporate 
to  dryness  and  filter.     Otherwise  add  ammonia  in  excess  to  the 
solution,  filter  off  the  precipitated  Fe2O3,  dissolve  the  latter  in  an 
excess  of  hydrochloric  acid,  and  determine  the  iron  as  directed 
on  page  277  or   dissolve   in   sulphuric  acid   and   determine   as 
directed  on  page  271. 

Lime. 

Heat  the  filtrate  from  the  iron  and  alumina  to  boiling  and  add 
an  excess  of  a  saturated  solution  of  ammonium  oxalate.  Stir  and 
boil  for  a  few  minutes  and  set  aside  for  several  hours  to  allow 
the  complete  precipitation  of  the  lime.  Filter,  wash,  dry,  and  ig- 
nite over  a  blast  lamp  until  the  weight  is  constant.  Weigh  as  cal- 
cium oxide,  CaO.  Or  determine  volumetrically  with  perman- 
ganate as  described  on  page  266. 

Magnesia. 

To  the  filtrate  from  the  calcium  oxalate  add  sufficient  hydro- 
chloric acid  to  make  it  slightly  acid  and  then  30  cc.  of  sodium 
phosphate  solution.  Concentrate  the  solution  to  about  200  cc.  by 
evaporation  and  cool.  Then  add  ammonia  drop  by  drop,  with 


THE    ANALYSIS    OF    THE    RAW    MATERIALS  34! 

constant  stirring  until  the  liquid  is  slightly  ammoniacal  and  the 
precipitate  begins  to  form.  Stop  adding  ammonia  and  stir  for 
five  minutes,  then  add  one-tenth  the  volume  of  the  liquid  of  strong 
ammonia  and  continue  the  stirring  for  five  minutes  more.  Allow 
the  solution  to  stand  in  a  cool  place  over  night,  filter,  wash  with 
a  mixture  of  1000  cc.  water,  500, cc.  ammonia  (sp.  gr.  0.96),  and 
150  grams  ammonium  nitrate.  Dry,  ignite  (do  not  use  the  blast 
lamp),  and  weigh  as  magnesium  pyrophosphate,  Mg2P2O7.  Mul- 
tiply this  by  0.36219  for  magnesium  oxide,  MgO. 

NOTES. 

Clay  is  practically  unacted  upon  by  hydrochloric  acid  and  requires 
fusion  with  alkaline  carbonates  for  its  decomposition. 

Should  the  solution,  on  evaporation  to  dryness,  show  a  tendency 
to  climb  the  sides  of  the  dish,  greasing  the  latter  lightly  with  vaseline  or 
paraffine  will  remove  the  difficulty. 

The  amounts  of  lime  and  magnesia  in  clays  are  small,  so  that  the 
filtrate  and  washings  from  the  second  ammonia  precipitation  of  the  iron 
and  alumina  may  be  rejected  and  the  lime  and  magnesia  determined  in 
the  first  filtrate  only.  For  the  same  reason  it  is  unnecessary  to  re- 
precipitate  the  calcium  oxalate,  although  the  solution  is  largely  con- 
taminated by  sodium  salts  from  the  alkaline  fusion. 

Determination  of  the  Alkalies. 

To  determine  the  alkalies  use  I  gram  of  the  clay,  i  gram  of  ammo- 
nium chloride  and  8  grams  of  calcium  carbonate  and  proceed  as  directed 
for  determining  the  alkalies  in  cement  on  page  300. 

Determination  of  Free,  Hydrated  and  Combined  Silica.1 

To  ascertain  how  much  of  the  silica  found  exists  in  combination 
with  the  bases  of  the  clay,  how  much  as  hydrated  acid,  and  how  much 
as  quartz  sand  or  as  a  silicate  present  in  the  form  of  sand,  proceed  as 
follows.9 

Let  A  represent  silica  in  combination  with  the  bases  of  the  clay. 

Let  B  represent  hydrated  silicic  acid. 

Let  C  represent  quartz  sand  and  silicates  in  the  form  of  sand,  e.  g., 
feldspar  sand. 

Dry  2  grams  of  the  clay  at  a  temperature  of  100°  C.,  heat  with  sul- 
phuric acid,  to  which  a  little  water  has  been  added,  for  eight  or  ten 
hours,  evaporate  to  dryness,  cool,  add  water,  filter  out  the  undissolved 
residue,  wash,  dry,  and  weigh  (A  -\-  B  -f-  C).  Then  treat  it  with 

1  Cairns'  Quantitative  Chemical  Analysis,  page  68. 

2  Compare  Fresenius'  Quantitative  Analysis,  sth  Ed.,  1865,  Sec.  236. 


342  PORTLAND  CEMENT 

sodium  carbonate.  Transfer  it,  in  small  portions  at  a  time,  to  a  boiling 
solution  of  sodium  carbonate  contained  in  a  platinum  dish,  boil  for 
some  time  and  filter  off  each  time,  still  very  hot.  When  all  is  trans- 
ferred to  the  dish,  boil  repeatedly  with  strong  solution  of  sodium  car- 
bonate until  a  few  drops  of  the  liquid  finally  passed  through  the  filter 
remain  clear  on  warming  with  ammonium  chloride.  Wash  the  residue, 
first  with  hot  water,  then  (to  insure  the  removal  of  every  trace  of 
sodium  carbonate  which  may  still  adhere  to  it)  with  water  slightly 
acidified  with  hydrochloric  acid,  and  finally  with  water.  This  will  dis- 
solve (A  -f~  B)  and  leave  a  residue  (C)  of  sand,  which  dry,  ignite, 
and  weigh. 

To  determine  (B),  boil  4  or  5  grams  of  clay  (previously  dried  at 
100°  C.)  directly  with  strong  solution  of  sodium  carbonate  in  a  platinum 
dish  as  above,  filter  and  wash  thoroughly  with  hot  water.  Acidify  the 
filtrate  with  hydrochloric  acid,  evaporate  to  dryness,  and  determine 
the  silica  as  usual.  It  represents  (B)  or  the  hydrated  silicic  acid. 

Add  together  the  weights  of  (B)  and  (C),  thus  found,  and  sub- 
tract the  sum  from  the  weight  of  the  first  residue  (A  +  B  +  C).  The 
difference  will  be  the  weight  of  (A)  or  the  silica  in  combination  with 
the  bases  of  the  clay. 

If  the  weight  of  (A  -j-  B  -f  C)  found  here  to  be  the  same  as  that 
of  the  silica  found  by  fusion  in  a  similar  quantity  in  the  analysis  of 
the  clay,  the  sand  is  quartz,  then  the  sand  contains  silicates. 

The  weight  of  the  bases  combined  with  silica  to  form  silicates  can 
be  found  by  subtracting  the  weight  of  total  silica  found  in  I  gram  in 
the  regular  analysis,  from  the  weight  (A  +  B  -f  C)  in  I  gram. 

NOTES. 

The  following  scheme  is  much  less  trouble  than  that  described  above 
and  gives  the  silica  present  as  sand  and  silicates  undecomposable  by  sul- 
phuric acid  and  that  in  combination  with  the  alumina  or  combined  silica. 

Heat  1.25  grams  of  the  finely  ground  and  dried  (at  100°  C.)  clay  with 
15  cc.  of  concentrated  sulphuric  acid  to  near  the  boiling-point  of  the 
acid  and  digest  for  from  ten  to  twelve  hours  at  this  temperature. 
Cool,  dilute  and  filter.  Wash  and  ignite  the  residue  to  a  constant 
weight.  Call  this  weight  A.  After  weighing  brush  the  residue  which 
consists  of  silica  present  as  sand  and  undecomposable  silicates  and  silica 
from  the  decomposition  of  the  silicates  of  alumina,  into  an  agate  mortar, 
grind  very  finely  and  weigh  0.5  gram  of  it  into  a  platinum  dish,  con- 
taining 50  cc.  of  boiling  caustic  potash  solution  (of  1.125  sp.  gr.).  Boil 
for  five  minutes,  filter,  wash,  first  with  hot  water  and  then  with  water 
containing  a  little  dilute  hydrochloric  acid  and  then  again  with  hot 
water,  dry  and  ignite  to  a  constant  weight.  Call  this  weight  B.  Multi- 
ply A  by  0.4  (to  correct  the  1.25  grams  of  clay  used  to  correspond  to 
the  0.5  gram  of  the  residue  taken  for  treatment  with  caustic  potash 


THE    ANALYSIS   OI?    THE   RAW    MATERIALS  343 

solution)  and  subtract  B  from  the  product.  Multiply  the  difference  by 
200  for  the  per  cent,  of  silica  combined  with  alumina  in  the  clay.  This 
deducted  from  the  total  silica  found  by  analysis  gives  the  silica  as  sand 
and  undecomposable  silicates. 

Determination  of  Coarse  Sand. 

In  examining  clay  to  be  used  for  cement  manufacture,  it  is  not 
so  important  to  know  the  chemical  condition  in  which  the  silica 
exists  as  its  physical  state,  i.  e.,  whether  the  sand  grains  are  large 
or  small.  Pure  quartz  sand  if  sufficiently  finely  powdered  will 
combine  with  lime  at  the  temperature  of  the  rotary  kiln,  so  that 
what  is  mo*t  requisite  in  clay  to  be  used  for  cement  manufacture 
is  that  the  sand  shall  be  present  in  fine  grains.  To  test  the  clay, 
along  this  line,  weigh  100  grams  of  clay  into  a  beaker  and  wet 
with  water.  Triturate  to  a  thin  slip  with  a  glass  rod  and  wash 
into  a  No.  100  test  sieve.  Now  place  the  sieve  under  the  tap  and 
wash  as  much  of  the  clay  as  possible  through  the  meshes  of  the 
sieve  with  a  gentle  stream  of  water.  Dry  the  sieve  on  a  hot-plate 
and  brush  out  the  dry  residue  failing  to  pass  through  it  on  to  the 
balance  pan  and  weigh.  The  weight  in  grams  gives  the  percent- 
age of  the  clay  failing  to  pass  a  No.  100  sieve.  The  clay  may  also 
be  tested  in  a  similar  manner  on  the  No.  200  sieve  and  the 
residues  may  be  subjected  to  chemical  analysis. 

Marls  are  examined  by  the  same  method  to  determine  fineness. 

Determination  of  Water  of  Combination. 

Should  the  clay  contain  very  little  organic  matter,  iron  pyrites 
or  calcium  carbonate,  heat  I  gram  of  the  previously  dried  cement 
for  twenty  minutes  to  a  bright  redness  over  a  Bunsen  burner. 
The  loss  in  weight  will  represent  the  water  of  combination.  If, 
however,  the  clay  contains  much  organic  matter,  calcium  carbon- 
ate or  iron  pyrites,  the  water  of  combination  should  be  de- 
termined by  absorption  in  a  weighed  calcium  chloride  tube  as 
described  for  cement  analysis  on  page  288. 

Many  chemists  simply  heat  I  gram  of  dried  clay  over  a  blast 
for  twenty  minutes  reporting  the  loss  of  weight  as  loss  on  igni- 
tion. This  loss,  of  course,  comes  from  combined  water  and  car- 
bon dioxide  driven  off  (from  the  decomposition  of  carbonates), 


344  PORTLAND  CEMENT 

organic  matter  burned  and  iron  pyrites  changed  from  iron  sul- 
phide, FeS2,  to  ferric  oxide. 

Sulphur  and  Iron  Pyrites. 

For  the  determination  of  sulphur  in  clay,  proceed  as  directed 
for  determining  this  constituent  in  cements  by  fusion  with  sodium 
carbonate  and  potassium  nitrate.  Multiply  the  weight  of  barium 
sulphate  by  0.25701  and  report  as  iron  pyrites,  FeS2,  or  by  0.13738 
and  report  as  sulphur.  If  reported  as  FeS2  multiply  the  percent- 
age of  this  latter  by  0.90836  and  deduct  from  the  Fe2O3. 

Rapid  Determination  of  Silica,  Iron  Oxide  and  Alumina  and  Lime. 

Weigh  0.5  gram  of  the  finely  ground  sample  of  clay  into  a 
platinum  crucible  and  mix  with  it  intimately,  by  stirring  with  a 
glass  rod  rounded  at  the  ends,  one  gram  of  precipitated  calcium 
carbonate  such  as  is  used  for  alkali  determinations  and  one-half 
gram  of  finely  powdered  dry  sodium  carbonate.  The  mixing  must 
be  thorough.  Brush  off  the  rod  into  the  crucible  with  a  camel's- 
hair  brush  and  place  the  covered  crucible  over  a  Bunsen  burner 
turned  low.  Gradually  raise  the  flame  till  the  full  heat  is  attained, 
keep  at  this  temperature  for  2  or  3  minutes,  and  then  remove  to 
the  blast  lamp  and  ignite  strongly  for  5  minutes.  Cool  the  cruci- 
ble by  plunging  its  bottom  in  cold  water  and  place  it  on  its  side  in 
a  platinum  or  porcelain  dish  or  casserole.  Add  10  cc.  of  water 
and  10  cc.  of  dilute  (i-i)  acid.  As  soon  as  the  mass  is  dissolved 
out  of  the  crucible  remove  the  latter,  rinse  it  off  into  the  dish 
removing  any  solid  particles  with  a  policeman  and  evaporate  the 
solution  to  dryness.  Heat  the  dish  at  120°  C.  until  all  odor  of 
acid  has  disappeared.  Cool,  add  20  cc.  of  hydrochloric  acid  (i-i), 
cover  and  boil  a  few  minutes,  add  50  cc.  of  water,  boil  a  few  min- 
utes longer,  filter,  wash  and  ignite,  first  over  the  burner,  until 
carbon  is  all  burned  off,  and  then  over  the  blast  for  10  minutes. 
Cool  and  weigh  as  silica,  SiO2. 

Iron  Oxide  and  Alumina. 

Heat  the  filtrate  to  boiling,  after  adding  a  few  drops  of  bromine 
water,  add  ammonia  in  slight  but  distinct  excess  and  again  heat  to 
boiling.  Continue  boiling  for  two  or  three  minutes  and  after 


THE    ANALYSIS    OF    THE    RAW    MATERIALS  345 

allowing  the  precipitate  to  settle,  filter  and  wash  once  with  hot 
water.  Invert  the  funnel  over  the  beaker  in  which  the  precipita- 
tion was  made  and  wash  the  precipitate  back  into  this  with  a 
stream  of  hot  water  from  a  wash-bottle.  Dissolve  in  dilute  nitric 
acid,  heat  to  boiling  and  reprecipitate  with  ammonia.  Boil  for  a 
few  minutes,  allow  the  precipitate  to  settle,  and  filter.  Wash  once 
with  hot  water,  ignite  (using  the  blast  finally)  and  weigh  as 
oxides  of  alumina  and  iron,  A12O3  +  Fe2O3. 

Lime. 

Weigh  another  sample  of  one  gram  into  a  platinum  dish  or  a 
large  crucible  and  add  10  cc.  of  dilute  sulphuric  acid  (i-i)  and 
approximately  5  cc.  of  hydrofluoric  acid.  Heat  until  fumes  of 
sulphuric  acid  come  off  copiously.  Cool  and  wash  the  contents  of 
the  dish  into  a  250  cc.  beaker.  Heat  to  boiling  and  add  ammonia 
in  slight  but  distinct  excess.  Redissolve  the  precipitate  in  10  cc. 
of  a  10  per  cent,  solution  of  nitric  acid,  and  dilute  to  200  cc. 
Precipitate  the  lime  with  ammonium  ovalate  as  usual  and  de- 
termine as  directed  on  page  266. 

METHODS  FOR  GYPSUM  OR  PLASTER  OF  PARIS. 

Determination  of  Silica,  Iron  Oxide,  Alumina,  Lime  and  Mag- 
nesia. 

Weigh  0.5  gram  of  the  finely  ground  sample  into  a  platinum 
dish  or  porcelain  casserole  and  add  20  cc.  of  dilute  hydrochloric 
acid  (i-i).  Evaporate  to  dryness  and  heat  the  residue,  at  no0 
C.  until  all  odor  of  hydrochloric  acid  has  vanished  from  the  con- 
tents of  the  dish.  Cool  and  add  10  cc.  of  dilute  hydrochloric  acid, 
cover  with  a  watch-glass  and  heat  for  5  minutes.  Dilute  to  50  cc. 
and  heat  a  little  longer.  Filter,  wash  the  precipitate  well  with  hot 
water,  ignite  and  weigh.  Report  as  insoluble  silicious  matter  or 
proceed  as  follows :  Ignite  0.5  gram  of  the  sample  with  ^2  gram 
of  pulverized  sodium  carbonate  first  over  a  burner  and  then  over 
a  blast.  Place  the  crucible  in  a  dish  or  beaker  and  dissolve  out 
the  mass  in  a  little  dilute  hydrochloric  acid.  Evaporate  the  solu- 
tion to  dryness  and  heat,  at  110°  C.,  until  all  odor  of  hydrochloric 
acid  has  disappeared  from  the  dry  mass.  Dissolve  in  a  little 


346  PORTLAND  CEMENT 

hydrochloric  acid  and  water,  as  before,  filter,  wash,  ignite  and 
weigh  as  SiO2. 

Heat  the  filtrate  from  the  SiO2  or  that  from  the  "insoluble 
silicious  matter,"  as  the  case  may  be,  to  boiling,  precipitate  the 
iron  and  aluminum  as  oxides  with  ammonia  and  proceed  as  in 
the  analysis  of  cements  on  page  256. 

Determination  of  Sulphuric  Acid. 

Weigh  0.25  gram  of  the  finely  ground  sample  into  a  beaker  and 
dissolve  in  5  cc.  of  dilute  (i-i)  hydrochloric  acid,  by  the  aid  of 
heat.  Dilute  to  100  cc.  with  hot  water.  Digest  for  a  few  minutes 
and  filter.  Wash  the  paper  and  residue  thoroughly,  with  hot 
water,  until  the  filtrate  measures  about  250  cc.  Heat  this  latter 
to  boiling  and  add,  with  constant  stirring,  20  cc.  of  barium  chlor- 
ide solution,  also  boiling  hot,  and  stir  for  five  minutes.  Remove 
from  the  source  of  heat  and  allow  to  stand  over  night  in  a  warm 
place.  In  the  morning,  filter  through  a  double  filter-paper  or  a 
"Shimer  filter  tube"1  and  wash  well  with  hot  water.  Ignite 
(without  using  the  blast)  and  weigh  as  BaSO4.  This  weight 
multiplied  by  0.34300  gives  the  SO3  in  the  sample  or  by  0.62184 
the  (CaSO4)  H2O  or  by  0.7375  the  CaSO4.  2H2O.  Do  not  for- 
get a  quarter  gram  sample  has  been  taken. 

The  above  method  is  that  generally  employed.  The  writer, 
however,  prefers  to  separate  the  lime  from  the  solution  before 
precipitating  the  sulphur.  His  method  is  as  follows :— Weigh 
0.25  gram  of  the  sample  into  a  small  beaker  and  add  5  cc.  of 
dilute  (i  :  i)  hydrochloric  acid.  Heat  until  solution  is  complete. 
Dilute  to  ipo  cc.  make  alkaline  with  ammonia  and  add  an  excess 
of  ammonium  carbonate  solution.  Boil  for  a  few  minutes  and 
filter.  Wash  the  residue  with  hot  water  and  redissolve  in  5  cc. 
of  acid.  Again  neutralize  with  ammonia  and  add  ammonium 
carbonate  solution.  Filter  and  wash  the  residue  with  hot  water 
a  few  times.  Combine  the  filtrates  from  the  two  precipitations. 
Acidify  with  hydrochloric  acid,  using  an  excess  of  about  3  or  4 
cc.  Heat  to  boiling  and  precipitate  the  sulphur  as  directed  above 
with  barium  chloride. 

1  See  page  286. 


THE    ANALYSIS   OF    THE   RAW    MATERIALS  .  347 

Determination  of  Water. 

Weigh  one  gram  of  the  finely  ground  sample  in  a  weighed 
platinum  crucible  and  heat1  for  one  hour  at  100-105°  C.  Cool 
and  weigh.  The  loss  in  weight  represents  the  "moisture"  or 
"water  below  105°  C." 

Determine  the  combined  water  and  carbon  dioxide  as  directed 
for  cement  on  page  288,  or: 

Place  the  crucible  over  a  Bunsen  burner  and  heat  at  a  low  red 
temperature  for  thirty  minutes.  The  loss  in  weight  represents 
"water  of  combination"  or  "water  above  105°  C."  If  the  heating 
has  been  too  high,  some  sulphuric  acid  will  have  also  been  lost. 
To  check  this,  dissolve  the  sample  out  of  the  crucible,  after  igni- 
tion, with  hydrochloric  acid.  Dilute  to  about  100  cc.  and  filter 
into  a  200  cc.  flask.  Wash' well  with  hot  water  and  dilute  with 
water  to  the  mark.  Measure  of  this  volume  50  cc.  dilute  to  250 
cc.  and  determine  the  SO3  as  directed  previously.  If  loss  has 
occurred,  this  determination  will  give  a  lower  figure  than 
the  other.  In  this  case  deduct  the  difference  between  the 
percentages  found  by  the  two  trials  from  percentage  of  loss  in 
weight  over  the  burner  for  the  percentage  of  water  of  combina- 
tion. If  the  heating  of  the  crucible  over  the  Bunsen  burner  has 
been  done  at  a  heat  not  higher  than  cherry-red  there  should  be 
no  loss  of  sulphuric  acid,  however. 

Determination  of  Carbon  Dioxide. 

Determine  carbon  dioxide  as  directed  on  page  296,  for  cement, 
using  the  evolution  method. 

>  See  page  298. 


PHYSICAL  TESTING. 


Chapter  XIII. 


THE  INSPECTION  OF  CEMENT. 

Standard  Specifications  for  Inspection. 

"i.     All  cement  shall  be  inspected. 

"2.  Cement  may  be  inspected  either  at  the  place  of  manu- 
facture or  on  the  work. 

"3.  In  order  to  allow  ample  time  for  inspecting  and  testing, 
the  cement  should  be  stored  in  a  suitable  weather-tight  building 
having  the  floor  properly  blocked  or  raised  from  the  ground. 

"4.  The  cement  shall  be  stored  in  such  a  manner  as  to 
permit  easy  access  for  proper  inspection  and  identification  of 
each  shipment. 

"5.  Every  facility  shall  be  provided  by  the  contractor  and  a 
period  of  at  least  twelve  days  allowed  for  the  inspection  and 
necessary  tests. 

"6.  Cement  shall  be  delivered  in  suitable  packages  with  the 
brand  and  name  of  manufacturer  plainly  marked  thereon. 

"7.  A  bag  of  cement  shall  contain  94  pounds  of  cement 
net.  Each  barrel  of  Portland  cement  shall  contain  4  bags,  and 
each  barrel  of  natural  cement  shall  contain  3  bags  of  the  above 
net  weight. 

"8.  Cement  failing  to  meet  the  seven-day  requirements  may 
be  held  awaiting  the  results  of  the  twenty-eight  day  tests  before 
rejection. 

"9.  All  tests  shall  be  made  in  accordance  with  the  methods 
proposed  by  the  Committee  on  Uniform  Tests  of  Cement  of  the 
American  Society  of  Civil  Engineers,  presented  to  the  Society 
January  21,  1903,  and  amended  January  20,  1904,  and  January 
14,  1908,  with  all  subsequent  amendments  thereto." 


THE   INSPECTION    OF   CEMENT  349 

Methods  of  Inspection. 

It  is  now  the  custom  to  test  carefully  all  cement  to  be  used 
upon  important  work.  Most  of  the  large  cities  of  the  country 
maintain  well  equipped  laboratories  and  systematically  inspect  all 
cement  used  upon  the  various  municipal  works  undertaken  by 
them.  The  various  branches  of  the  government,  such  as  the  War, 
Navy  and  Treasury  Departments,  each  have  one  or  more  labora- 
tories where  the  cement  to  be  used  in  fortifications,  dry-docks, 
public  buildings,  etc.,  is  carefully  tested.  Various  private  labora- 
tories also  make  a  specialty  of  inspecting  the  cement  to  be  used  in 
big  buildings,  reservoirs,  retaining  walls,  etc.,  for  private  corpora- 
tions, while  the  railroads,  most  of  them,  have  well  equipped 
laboratories  for  testing  such  materials,  cement  among  them,  as 
they  purchase.  Cement  may  be  inspected  either  at  the  mill  before 
shipment,  or  at  the  place  where  it  is  to  be  used,  after  receipt.  The 
actual  tests,  of  course,  may  be  made  at  either  of  these  points,  or  the 
samples  can  be  properly  labelled  and  sent  some  distance  to  a  con- 
venient laboratory.  The  New  York  Rapid  Transit  Railroad 
(Subway)  Commission  pursued  the  former  of  these  two  plans 
and  inspected  the  cement  at  the  mill  itself.  The  Philadelphia 
Rapid  Transit  Company,  on  the  other  hand,  followed  the  latter 
plan  and  inspected  the  cement  as  received  in  Philadelphia.  Both 
plans  can  be  made  to  give  entire  satisfaction. 

Where  the  product  of  one  mill  alone  is  to  be  used  for  the  work, 
the  testing  laboratory  may  be  located  at  the  mill  from  which  the 
cement  is  supplied.  Otherwise,  it  should,  of  course,  be  located  at 
some  convenient  point  to  which  samples  can  readily  be  sent. 

The  suggestion  has  been  made  that  the  cement  companies 
furnish  the  inspector  testing  appliances,  quarters,  etc.,  for  doing 
this  work.  This  seems  to  be  asking  rather  much  of  the  manufac- 
turers, as  their  laboratories  are,  most  of  them,  already  over- 
crowded and  the  presence  of  an  outsider,  in  the  one  part  of  the 
plant  where  trade  secrets  are  likely  to  be  exposed,  is  not  desirable. 

Inspection  at  the  Mill. 

Where  cement  inspection  is  done  at  the  mill,  certain  bins  are 
set  aside  by  the  proper  authority  at  the  cement  mill,  and  the 


35O  PORTLAND 

spouts  leading  into  these  are  closed  by  means  of  a  wire  and  lead 
seal  such  as  is  used  in  closing  box  cars ;  the  idea  of  sealing  the 
spouts  is  to  prevent  the  bins  from  being  emptied  and  refilled 
without  the  knowledge  of  the  inspector.  Any  method  which 
will  insure  against  this.,  such  as  sealing  wax  and  string  will 
answer  as  well  as  the  lead  seal  and  wire.  In  some  cases,  it 
may  be  sufficient  to  rely  upon  the  honesty  of  the  mill  authorities 
and  to  merely  accept  their  word  or  promise  that  the  bin  has  not 
been  tampered  with.  Or  an  affidavit  may  be  secured  from  the 
stock-house  foreman  to  this  effect. 

After  selecting  the  bin  and  insuring  against  its  being  emptied 
and  refilled,  it  must  be  carefully  sampled.  How  this  is  to  be 
done  will  depend  somewhat  upon  the  size  and  shape  of  the  bin. 
Since  cement  when  freshly  ground  and  hot  flows  not  unlike  a 
liquid,  the  cement  first  run  into  the  bin  will  be  almost  all  of  it 
deposited  in  a  layer  on  the  floor  of  the  bin.  For  this  reason,  the 
means  used  for  sampling  the  bin  must  be  such  that  the  cement  at 
the  bottom  of  the  bin  is  included  in  the  sample.  On  page  355, 
a  rod  such  as  is  used  by  the  inspectors  of  the  Baltimore  &  Ohio 
Railroad  is  described.  This  is  probably  as  satisfactory  as  any 
sampling  device  can  well  be.  The  taking  of  a  sample  from  the 
floor  of  a  bin  may  necessitate  the  use  of  a  sledge  hammer  to 
drive  the  rod  through  the  mass  of  cement  in  the  bin.  If  the 
inspector  is  permanently  located  at  the  mill,  the  sample  can  be 
taken  easiest,  when  the  bin  is  being  filled,  by  means  of  an  auto- 
matic sampler  such  as  is  described  on  page  306. 

The  importance  of  sampling  the  floor  of  a  bin  will  be  under- 
stood, when  it  is  known  that,  in  a  bin  of  unsound  cement,  a 
sample  taken  only  a  few  days  after  the  bin  has  been  filled  and 
representing  only  the  surface  layer  of  cement  will  often  be  sound, 
while  one  representing  the  bottom  layer  may  be  unsound  after 
even  a  month's  seasoning. 

The  bin  should  be  sampled  in  at  least  four  places — the  four 
corners — and  may  be  sampled  in  as  many  more  as  the  inspector 
sees  fit.  A  sample  drawn  from  the  four  corners  of  rectangular 
shaped  bins,  filled  by  a  spout  in  the  middle,  will  be  representative. 


THE  INSPECTION  OF  CEMENT  351 

The  feet  and  legs  of  the  man  taking  the  sample  may  be  pro- 
tected as  he  walks  over  the  surface  of  the  cement  by  thrusting 
them  in  clean  new  cloth  cement  bags  (a  few  of  which  can  be 
found  around  all  mills)  and  tying  them  securely  around  the  legs 
above  the  knee.  The  cement  sample  should  be  placed  in  clean 
cloth  bags,  which  should  be  properly  closed  and  sealed  and  ex- 
pressed or  conveyed  to  the  testing  laboratory.  If  the  inspecting 
laboratory  is  located  at  the  mill,  paper  bags  or  tin  buckets  may 
be  used  for  this  purpose.  Small  milk  cans  holding  about  4 
quarts  will  be  found  excellent  for  transporting  samples,  as  the 
tops  can  be  wired  down  tight  and  the  samples  are  protected  from 
changes  due  to  exposure  to  air  in  them. 

The  objection  has  been  raised  to  the  use  of  cloth  bags,  that  an 
unsound  cement  would  probably  be  seasoned  sound  after  a  two  or 
three  days  journey  in  them  and  some  inspectors  use  tin  buckets 
or  cans,  with  tightly  fitting  covers  for  this  purpose.  On  the  other 
Irand,  if  an  unsound  sample  is  made  sound  by  exposure  in  cloth 
bags  after  a  few  days  journey  by  express,  the  inspector  may  rest 
assured  that  the  body  of  the  bin  will  be  seasoned  equally  well  by 
an  equally  long  journey  by  freight  in  a  box  car.  Also  cement 
often  leaves  the  mill  "slow-setting"  and  arrives  at  the  work 
"quick-setting/'  so  that  shipment  of  a  sample  in  cloth  should  give 
a  line  on  the  likelihood  of  the  main  body  of  the  cement  doing  this. 

When  the  sample  arrives  at  the  testing  laboratory,  its  receipt 
is  properly  recorded  together  with  such  data  as  the  brand, 
manufacturer,  bin,  date  sampled,  etc.,  after  which,  to  readily 
identify  briquettes,  etc.,  it  is  given  a  running  number.  The 
sample  is  then  carefully  mixed,  and  a  sufficient  quantity  of  this 
for  the  necessary  tests  is  taken  and  passed  through  a  2o-mesh 
sieve  to  remove  lumps,  after  which  it  is  submitted  to  the  tests 
called  for  by  the  specifications.  The  large  sample  is  then  stored 
away  in  a  tin  can  or  a  fruit  jar  for  future  reference,  re-tests,  etc. 

When  the  results  of  the  tests  are  at  hand,  the  laboratory  noti- 
fies its  agent  at  the  mill,  who  in  turn  informs  the  authorities  of 
the  cement  company  that  such  and  such  a  bin  is  ready  for  ship- 
ment, and  when  cement  is  needed  it  is  also  the  duty  of  the  mill 


352  PORTLAND  CEMENT 

inspector  to  see  that  the  cement  is  packed  from  accepted  bins 
and  accepted  bins  only. 

This  system  usually  necessitates  the  holding  of  a  bin  for  from 
five  to  six  weeks,  if  the  specifications  call  for  a  28-day  test,  or 
about  two  weeks  if  only  the  7-day  test  is  relied  upon.  This  often 
puts  the  manufacturer  to  much  inconvenience  and  trouble,  but, 
from  the  standpoint  of  the  consumer,  seems  to  be  preferable, 
since  the  manufacturer  pays  for  the  storage  while  the  cement  is 
being  tested.  On  the  other  hand  the  manufacturer  has  the 
satisfaction  of  knowing  that,  after  the  cement  is  once  shipped, 
it  is  off  his  hands  for  good  and  all  with  no  chance  for  complaint 
from  the  purchaser. 

Another  form  of  inspection  at  the  mill  consists  in  sampling 
the  cars  as  they  are  filled.  This  is  usually  done  by  taking  a 
small  quantity  of  cement  from  one  in  every  40  to  50  bags 
packed.  These  small  samples  are  then  either  mixed  or  not  as 
desired  and  sent  to  the  laboratory  for  tests.  The  car  is  not  held 
for  the  result  of  these  but  is  immediately  billed  to  its  destina- 
tion. By  the  time  it  has  reached  this  the  7-day  tests  will  usually 
have  been  completed.  If  the  tests  are  satisfactory  the  car  can  be 
immediately  unloaded  and  used.  This  method  is  employed  by 
most  testing  laboratories. 

Inspection   on   the    Work. 

When  the  cement  is  inspected  as  it  arrives  at  the  work,  the 
cars  are  unloaded  and  sampled — one  bag  out  of  every  40  (or  one 
barrel  in  ten)  being  selected  and  a  sample  drawn  from  it  as  indi- 
cated on  page  354.  These  samples  may  be  either  mixed  or  kept 
separate  in  clean  paper  bags.  The  contents  of  each  car  should  be 
piled  in  such  a  way  that  it  may  be  kept  to  itself  and  marked  by 
a  properly  tagged  board  or  sign.  When  the  work  permits  the 
use  of  a  large  store  house,  this  should  be  divided  into  bins  hold- 
ing a  carload,  150  barrels  or  600  bags.  The  cement  should  be 
held  in  storage  until  the  results  of  the  tests  are  known  when,  if 
these  are  satisfactory,  the  contractor  or  foreman  may  be  notified 
that  he  can  use  the  cement  from  such  and  such  a  pile  or  bin. 


THE;  INSPECTION  OF  CEMENT  353 

When  a  car  of  cement  fails  to  pass  the  specifications,  the  manu- 
facturer is  usually  notified  at  once  that  such  cement  has  been 
found  unsatisfactory.  He  will  then  probably  ask  for  a  re-test, 
which  should  be  made  from  new  samples,  drawn  in  the  presence 
of  his  representatives,  and,  if  possible,  the  tests  also  should  be 
repeated  in  the  presence  of  this  representative.  If  this  latter  can 
not  be  done,  the  sample  should  be  divided  into  three  parts  and 
placed  in  tin  cans  or  fruit  jars  and  closed  up  tight.  One  of  these 
samples  should  be  tested  by  the  manufacturer  and,  unless  his  re- 
sults agree  with  those  of  the  consumer,  the  third  sample  should 
be  sent  to  some  reliable,  competent  third  party  with  the  agree- 
ment of  both  manufacturer  and  consumer  to  stand  by  his  results. 

Should  the  cement  finally  be  found  unsatisfactory,  it  is  usually 
returned  to  the  manufacturer,  who  replaces  it  with  another  con- 
signment or  else  a  rebate  is  given  upon  it  and  it  is  used  on  some 
unimportant  part  of  the  job.  Uusound  cement  may  be  held  until 
it  has  been  seasoned  sound  and  quick-setting  cement  may  often  be 
made  slow-setting  by  a  small  addition  (0.5  per  cent.)  of  plaster 
or  slaked  lime.  In  both  instances,  the  resulting  concrete  will  be 
satisfactory  and  the  manufacturer  will  usually  be  willing  to  bear 
the  expense  of  storage,  or  addition  of  plaster  or  lime,  rather  than 
pay  the  double  freight,  necessary  to  its  replacement  with  other 
cement. 

When  the  cement  supplied  by  a  manufacturer  habitually  fails 
to  pass  the  specifications  under  which  it  is  sold,  he  deserves 
little  consideration  from  the  engineer  or  inspector,  but,  when 
the  failure  of  a  brand  to  meet  specifications  is  a  rare  incident, 
the  engineer  can  afford  to  be  lenient,  if  his  work  is  not  en- 
dangered thereby,  especially  if  the  average  quality  of  the  cement 
is  far  above  that  asked  for  by  him,  in  his  specifications. 

Standard  Methods  of  Sampling. 

The  methods  of  sampling  recommended  by  the  committee  on 
cement  testing  of  the  American  Society  of  Civil  Engineers  are 
as  follows: 

"i. — SELECTION  OF  SAMPLE. — The  selection  of  the  sample  for 
testing  is   a  detail  that  must  be  left  to  the   discretion   of  the 
23 


354  PORTLAND  CEMENT 

engineer;  the  number  and  the  quantity  to  be  taken  from  each 
package  will  depend  largely  on  the  importance  of  the  work,  the 
number  of  tests  to  be  made  and  the  facilities  for  making  them. 

"2. — The  sample  shall  be  a  fair  average  of  the  contents  of 
the  package;  it  is  recommended  that,  where  conditions  permit, 
one  barrel  in  every  ten  be  sampled. 

"3. — Samples  should  be  passed  through  a  sieve  having 
twenty  meshes  per  linear  inch,  in  order  to  .break  up  lumps  and 
remove  foreign  material ;  this  is  also  a  very  effective  method  for 
mixing  them  together  in  order  to  obtain  an  average.  For  de- 
termining the  characteristics  of  a  shipment  of  cement,  the  individ- 
ual samples  may  be  mixed  and  the  average  tested;  where  time 
will  permit,  however,  it  is  recommended  that  they  be  tested 
separately. 

"4. — METHOD  OF  SAMPLING. — Cement  in  barrels  should  be 
sampled  through  a  hole  made  in  the  center  of  one  of  the  staves, 
midway  between  the  heads,  or  in  the  head,  by  means  of  an  auger 
or  a  sampling  iron  similar  to  that  used  by  sugar  inspectors.  If 
in  bags,  it  should  be  taken  from  surface  to  center." 

The  knowledge  usually  sought  by  a  test  and  analysis  of  cement 
is  the  average  composition  and  properties  of  a  given  lot  or  bin. 
In  order  that  it  shall  give  this,  it  is  necessary  that  the  small; 
sample  used  in  the  tests  shall  fairly  represent  the  whole  quantity, 
possibly  many  tons.  In  a  large  lot  of  cement,  it  often  happens 
that  a  small  sample,  or  even  a  large  sample,  taken  from  one 
place  in  the  bin  or  one  barrel  in  the  consignment,  will  not  rep- 
resent the  cement,  since  this  particular  point  in  the  bin,  or  this 
special  barrel,  might  be  better  or  worse  than  the  remainder.  It 
is  well  in  sampling  from  a  bin,  to  take  small  samples  from  various 
points,  not  merely  upon  the  surface  where  the  cement  may  have 
become  slightly  altered  by  exposure  to  air  or  damp,  but  also  un- 
derneath by  using  a  fairly  long  brass  tube,  or  some  other  form  of 
sampler,  such  as  will  be  described  hereafter. 

In  sampling  shipments  it  is  best  to  take  a  sample  from  ten  or 
more  bags  or  barrels  in  each  one  hundred  barrels. 


THE   INSPECTION   OF   CEMENT 


355 


Samplers. 

In  sampling  cement  from  a  bag  or  barrel  a  small  brass  tube 
with  a  slit  cut  down  the  middle  may  be  used.  The  slit  is  neces- 
sary as  the  cement  becomes  packed  in  the  tube  when  it  is  thrust 
into  the  cement  and  it  is  necessary  to  run  a  lead  pencil  or  nail  up 
and  down  the  opening  to  get  the  cement  out.  The  tube  for  this 
purpose  need  not  be  over  two  feet  long  and  its  upper  end  should 
be  screwed  into  a  T,  the  latter  forming  a  handle.  The  forms  of 
grain  and  sugar  samplers  sold  by  dealers  in  apparatus  for  cement 
testing  may  be  used  for  sampling  bags  and  barrels. 

In  sampling  cement  packed  in  Bates  valve  bags,  this  can  be 
done  without  untying  the  bags  by  thrusting  a  brass  tube  into  the 


j 

Fig.  109. — Jointed  sampling  rod. 

contents  of  the  bag  through  the  valve.  See  page  231.  The  spill 
from  the  tube  of  this  machine  will  also  make  a  good  average 
sample  of  bags  packed. 

For  sampling  bins  of  cement  in  the  stock  houses  at  the  mill  the 
depth  of  the  former,  often  eight  or  more  feet,  makes  their  proper 
sampling  a  difficult  matter  unless  a  specially  devised  sampling  rod 
is  at  hand.  In  order  to  get  an  average  of  the  bin  it  is  necessary 
to  draw  portions  from  it  at  all  depths  and  at  both  ends.  An 
excellent  apparatus  for  doing  this,  consists  of  a  long  iron  rod 
such  as  is  shown  in  Fig.  109. 


356  PORTLAND  CEMENT 

It  is  made  of  I  inch  wrought  iron  piping  and  in  sections  of 
about  four  feet  each,  to  allow  of  its  being  readily  carried  about 
from  one  mill  to  another.  The  couplings  are  long  and  are  turned 
down  so  as  to  taper  at  either  end.  In  the  end  of  the  rod  is 
fastened  a  steel  point  and  slots  about  ]/\  inch  in  width  and  four- 
teen inches  in  length  are  cut  in  each  section  as  shown  in  the 
illustration.  One  side  of  each  slot  is  made  to  project  slightly 
beyond  the  side  of  the  pipe  and  sharpened,  as  shown  in  the  sec- 
tion A-B.  In  using  the  rod,  as  many  sections  are  used  as  may 
be  necessary  to  reach  to  the  bottom  of  the  bin.  These  are  joined, 
the  whole  is  thrust  into  the  bin  until  it  reaches  the  bottom,  the 
rod  is  rilled  by  turning  it  a  few  times,  then  withdrawn,  turned 
upside  down  and  the  cement  shaken  out  of  it  into  a  bag  by 
rapping  it  against  the  side  of  the  stock  house. 

A  rod  made  with  the  slot  running  its  entire  length  and  termi- 
nating in  a  Tf  with  two  pieces  of  short  pipe  screwed  into  it  to 
form  a  handle,  is  sometimes  used  to  sample  bins.  The  main 
trouble  with  this  rod  is  that  such  a  long  slot  weakens  the  sampler, 
and  unless  made  of  very  heavy  pipe  it  soon  twists  out  of  shape. 
Grain  samplers  may  also  be  used  to  sample  bins  but  are  seldom 
made  long  enough  to  reach  to  the  bottom  of  the  bins. 

Fig.    no  shows   a   sampler  designed  by  Mr.   Wm.   P.   Gano, 


Fig.  i io.— Sampling  rod  designed  by  Wm.  P.  Gano. 

chief  chemist  of  the  Pennsylvania  Cement  Co.,  and  made  by 
Riehle  Bros.  Testing  Machine  Co.  It  consists  of  two  brass 
tubes,  io  ft.  long,  one  of  which  fits  snugly  into  the  other.  The 
outside  tube  is  1^4  inches  outside  diameter.  Two  bronze  handles 
are  pinned,  one  to  each  tube,  and  the  outside  tube  is  provided 
with  a  bronze  point.  The  outside  tube  is  No.  20  brass  and  the 
inside  No.  16.  Both  tubes  are  provided  with  27  openings,  2^2 


THE   INSPECTION    OF   CEMENT 


357 


inches  long  by  ^  inch  wide.  These  slots  are  made  at  correspond- 
ing points  in  the  two  tubes.  One  edge  of  each  slot  in  the  out- 
side tube  is  flared  outward  and  provided  with  a  cutting  edge. 
A  Y$  inch  brass  set  screw  working  in  a  slot  shows  when  the 
openings  are  opposite.  The  sampler  is  thrust  down  into  the 
cement  with  the  inner  tube  turned  so  that  the  openings  are 
closed.  When  the  bottom  of  the  bin  is  reached,  the  handles  are 
turned  so  that  the  openings  are  opened  and  the  tube  is  turned 
round  a  few  times.  The  flared  edges  of  the  openings  then 
scrape  the  cement  into  the  tube.  This  sampler  is  one  of  the  best 
for  obtaining  a  sample  from  bins. 

Where  cement  can  be  sampled  as  it  goes  into  the  bin,  as  is 
done  regularly  by  the  manufacturer,  some  form  of  automatic 
sampler  such  as  described  on  page  306  should  be  installed  and  no 
mill  is  complete  which  is  not  so  equipped. 

A  vacuum  sampling  apparatus  invented  by  Bertram  Blount, 
the  English  cement  expert,  is  described  in  THE  CHEMICAL  ENGI- 
NEER, January,  1905,  p.  161,  which  consists  first  of  a  small  iron 


Fig.  in.— Blount's  vacuum  sampler. 

pipe  some  ^-inch  in  bore,  with  one  end  closed  and  drawn  to  a 
point.     The  other  end  is  open,  and  to  it  can  be  attached  a  length 


358  PORTLAND  CEMENT 

of  rubber  tubing.  The  pointed  end  of  the  pipe  has  a  number  of 
small  holes  pierced  in  it,  and  to  take  a  sample  this  tube  is  thrust 
into  the  heap  of  cement.  It  may  be  pushed  in  at  any  angle  from 
vertical  downwards.  The  india-rubber  tube  above  referred  to  is 
connected  to  a  drum  provided  with  an  opening  covered  with  a 
screw  cap,  the  whole  being  made  air-tight.  The  apparatus  is 
completed  by  means  of  an  exhausting  pump  which  may  either  be 
worked  by  hand  or  by  a  small  motor.  It  is  also  connected  to  the 
drum  by  a  length  of  rubber  tubing.  Each  length  of  rubber  tub- 
ing is  provided  with  a  screw*  slip,  which  can  be  made  to  nip  the 
tubing  so  tightly  that  no  air  can  get  past. 

In  sampling,  the  iron  pipe  is  plunged  nearly  to  the  bottom  of 
the  cement.  The  amount  of  cement  which  is  forced  through  the 
small  holes  in  the  lower  end  of  the  pipe  during  this  process  is  so 
small  that  it  may  be  neglected.  The  clip  on  the  rubber  tube  join- 
ing the  sampling  pipe  with  the  drum  is  then  screwed  up.  A  man 
then  worked  the  pump,  and  exhausts  the  drum  until  a  vacuum 
equal  to  some  18  or  20  inches  of  mercury  has  been  produced, 
when  the  clip  on  the  tube  between  the  drum  and  the  pump  is 
screwed  up.  The  drum  has  fitted  to  it  a  gauge,  so  that  the 
amount  of  vacuum  in  it  may  be  readily  seen.  The  clip  on  the 
tube  between  the  sampling  pipe  and  the  reservoir  drum  is  then 
unscrewed,  with  the  result  that  a  certain  amount  of  cement  will 
be  drawn  through  the  small  holes  in  the  sampling  pipe,  up 
through  the  latter,  and  then  conveyed  thence  through  the  rubber 
tube  to  the  reservoir.  The  whole  process  takes  but  a  minute  or 
two,  and  the  amount  drawn  into  the  reservoir  varies  with  the 
vacuum  produced.  Several  samples  may  be  taken  if  desirable, 
and  the  whole  operation  requires  but  half  an  hour. 

Uniform  Specifications  and  Methods  of  Testing, 

In  order  to  bring  about  uniformity  both  in  the  matter  of  in- 
spection and  of  the  specifications  under  which  cement  is  sold, 
committees  have  been  appointed  by  various  scientific  societies, 
chief  of  which  have  been  the  American  Society  for  Testing  Mate- 
rials and  the  American  Society  of  Civil  Engineers.  The  latter 


THE   INSPECTION    OF   CEMENT  359 

society  appointed  a  committee,  some  twenty  years  ago,  to  conr 
sider  methods  of  testing  cement  and  received  its  report  in  1885. 
Later,  another  committee  was  appointed,  which  reported  January 
21,  1903.  This  report  was  amended  at  various  times  to  keep  it 
up  to  date  and  the  methods  of  test  recommended  by  it  are  now 
considered  the  standard  ones. 

The  American  Society  for  Testing  Materials  turned  its  atten- 
tion to  the  drafting  of  a  uniform  set  of  specifications  for  cement, 
and  its  committee  first  reported,  June  17,  1904.  Since  this  time 
the  report  has  been  amended  a  number  of  times.  The  important 
amendments  consisted  in  altering  the  requirements  as  to  specific 
gravity  and  tensile  strength.  This  set  of  specifications  was 
endorsed  by  The  American  Institute  of  Architects,  The  Ameri- 
can Railway  Engineering  and  Maintenance  of  Way  Association, 
The  Association  of  American  Portland  Cement  Manufacturers, 
and  The  American  Society  of  Civil  Engineers,  and  hence  may 
be  considered  the  "Standard  Specifications." 

In  the  following  sections  under  the  heading  "Specification'  are 
given  the  requirements  as  defined  by  the  above  set  of  specifica- 
tions while  under  the  heading,  "Method  of  Operating  the  Test," 
is  given  the  method  of  testing  recommended  by  the  committee  of 
the  American  Society  of  Civil  Engineers  in  its  report. 

Tests  to  be  Made. 

The  qualities  which  are  requisite  for  a  good  Portland  cement 
are  those  which  insure  that  concrete  made  from  it  shall  be  of 
sufficient  strength  to  withstand  any  and  all  strains,  stresses  and 
shocks  to  which  it  may  be  submitted,  not  only  when  first  made 
and  allowed  to  harden,  but  aften  the  lapse  of  many  years.  The 
tests  now  applied  to  cement  all  aim  to  search  out  these  qualities, 
or  show  their  absence,  and  may  be  classed  under  two  general 
heads,  i.e.,  those  designed  to  show  the  strength  of  concrete  made 
from  the  cement,  and  those  designed  to  show  its  endurance. 
Under  the  first  head  come  the  tests  for  tensile  strength,  com- 
pressive  strength,  fineness  to  which  the  cement  is  ground,  as  this 
influences  its  sand  carrying  capacity  and  hence  its  strength,  and 


360  PORTLAND  CEMENT 

time  or  rate  of  setting,  as  quick-setting  cement  may  not  give 
sufficient  time  for  proper  manipulation  of  the  concrete  and  slow- 
setting  cement  may  take  too  long  to  get  its  strength.  Under  tests 
for  endurance  come  the  various  so-called  soundness  tests,  and 
possibly  chemical  analysis  as  the  quantities  of  magnesia  and  of 
sulphur  trioxide  present  are  supposed  to  have  an  influence  upon 
endurance. 

Ordinarily  cement  is  tested  as  to  its : 

1 i )  Soundness. 

(2)  Time  of  setting. 

(3)  Tensile  strength  alone    (neat). 

(4)  Tensile  strength  with  sand. 

(5)  Fineness  to  which  it  has  been  ground. 

(6)  Specific  gravity. 

Other  tests  are  those  of  compressive  and  transverse  strength, 
adhesion,  abrasion,  etc. 


Chapter  XIV. 


SPECIFIC  GRAVITY. 


Standard  Specifications  and  Method  of  Test. 

Specification. — The  specific  gravity  of  the  cement,  thoroughly 
dried  at  100°  C.,  shall  be  not  less  than  3.10.     Should  the  test 


Fig.  us.— I<e  Chatelier's  specific  gravity  apparatus. 

of  cement  as  received  fall  below  this  requirement  a  second  test 


362  PORTLAND  CEMENT 

may  be  made  upon  a  sample  ignited  at  a  low  red  heat.  The 
loss  in  weight  of  the  ignited  cement  shall  not  exceed  4  per  cent. 

Significance. — The  specific  gravity  of  cement  is  lowered  by 
adulteration  and  hydration,  but  the  adulteration  must  be  in  con- 
siderable quantity  to  affect  the  results  appreciably. 

In  as  much  as  the  differences  in  specific  gravity  are  usually 
very  small,  great  care  must  be  exercised  in  making  the  deter- 
mination. 

Method  of  Operating  the  Test. — The  determination  of  specific 
gravity  is  most  conveniently  made  with  Le  Chatelier's  apparatus. 
This  consists  of  a  flask  (D),  Fig.  112,  of  120  cu.  cm.  (7.32  cu. 
ins.)  capacity,  the  neck  of  which  is  about  20  cm.  (7.87  ins.) 
long;  in  the  middle  of  this  neck  is  a  bulb  (C),  above  and  below 
which  are  two  marks  (F)  and  (H)  ;  the  volume  between  these 
marks  is  20  cu.  cm.  (1.22  cu.  ins.).  The  neck  has  a  diameter 
of  about  9  mm.  (0.35  in.),  and  is  graduated  into  tenths  of  cubic 
centimeters  above  the  mark  (F). 

Benzine  (62°  Baume  naphtha)  or  kerosene  free  from  water, 
should  be  used  in  making  the  determination. 

The  specific  gravity  can  be  determined  in  two  ways: 

(1)  The  flask  is  filled  with  either  of  these  liquids  to  the  lower 
mark  (£),  and  64  gr.    (2.25  oz.)   of  powder,  previously  dried 
at  100°  C.  (212°  F.)  and  cooled  to  the  temperature  of  the  liquid, 

^      is  gradually  introduced   through  the   funnel   (B)    [the  stem  of 
W"which  extends  into  the  flask  to  the  top  of  the  bulb  (C)],  until 
the  upper  mark  (F)   is  reached.     The  difference  in  weight  be- 
tween the  cement  remaining  and  the  original  quantity   (64  gr.) 
is  the  weight  which  has  displaced  20  cu.  cm. 

(2)  The  whole  quantity  of  the  powder  is  introduced,  and  the 
level  of  the  liquid  rises  to  some  division  of  the  graduated  neck. 
This  reading  plus  20  cu.  cm.  is  the  volume  displaced  by  64  gr.  of 
the  powder. 

The  specific  gravity  is  then  obtained  from  the  formula : 

Weight  of  Cement 
Specific  Gravity^  Displaced  Volume 

The  flask,  during  the  operation,  is  kept  immersed  in  water  in  a 


SPECIFIC    GRAVITY  363 

jar  (A),  in  order  to  avoid  variations  in  the  temperature  of  the 
liquid.  The  results  should  agree  within  o.oi.  The  determina- 
tion of  specific  gravity  should  be  made  on  the  cement  as  received ; 
and  should  it  fall  below  3.10  a  second  determination  should  be 
made  on  the  sample  ignited  at  a  low  red  heat. 

A  convenient  method  for  cleaning  the  apparatus  is  as  follows : 
The  flask  is  inverted  over  a  large  vessel,  preferably  a  glass  jar, 
and  shaken  vertically  until  the  liquid  starts  to  flow  freely;  it  is 
then  held  still  in  a  vertical  position  until  empty;  the  remaining 
traces  of  cement  can  be  removed  in  a  similar  manner  by  pouring 
into  the  flask  a  small  quantity  of  clean  liquid  and  repeating  the 
operation. 

More  accurate  determination  may  be  made  with  the  pycnom- 
eter. 

Notes  on  the  Standard  Method. 

Kerosene  will  be  found  the  most  convenient  liquid  for  use 
iir  taking  the  specific  gravity  of  cement.  It  is  cheap  and  may  be 
easily  obtained.  To  free  it  from  water,  place  in  a  large  bottle, 
together  with  some  powdered  quicklime  and  shake  well.  Allow 
the  lime  to  settle,  keep  tightly  corked  and  draw  or  pour  off  the 
oil  carefully  for  use. 

Fig.  113  shows  a  new  form  of  Le  Chatelier's  apparatus 
designed  by  the  writer.  Its  peculiar  features  are  that  the  small 
bulb  is  made  pear  shape.  This  allows  the  cement  to  drop 
naturally  into  the  lower  bulb  and  prevents  the  stopping  up  of 
the  flask  at  the  lower  part  of  the  small  bulb,  which  often  happens 
with  the  older  form  of  apparatus.  Another  feature  of  the  bottle 
makes  it  of  use  to  the  chemist  at  the  cement  plant,  where  it  very 
often  happens  that  cement  is  obtained  with  a  specific  gravity 
higher  than  3.20.  In  the  new  bottle  the  bulb  itself  contains  only 
19.5  cc.,  the  graduation  of  the  stem  beginning  at  the  latter  point, 
and  thus  the  range  of  the  apparatus  is  extended  to  cements  hav- 
ing a  specific  gravity  as  high  as  3.28. 

In  making  a  determination  with  this  bottle,  the  writer  has 
usually  pursued  the  following  plan:  The  bottle  is  filled  with 
kerosene  to  slightly  above  the  mark  on  the  lower  stem  of  the 


364 


PORTLAND  CEMENT 


bottle.  The  bottle  and  the  sample  of  cement  whose  specific  grav- 
ity is  desired,  are  then  placed  side  by  side  on  a  table  and  allowed 
to  remain  there  for  one-half  hour.  At  the  end  of  this  time, 
a  thermometer  is  placed  in  the  flask  with  its  bulb  well 
down  in  the  lower  bulb  of  the  latter.  As  soon  as  the 

V7 


Fig.  113.— Meade's  improved  form  of  Le  Chatelier's  apparatus. 

temperature  is  constant,  the  reading  is  taken,  the  thermometer 
withdrawn,  the  oil  sucked  off  by  means  of  a  piece  of  glass  tubing 
(drawn  out  to  form  a  small  pipette)  until  it  reaches  the  lower 
bulb  of  the  stem.  A  funnel  is  then  inserted  into  the  upper  stem 
of  the  apparatus  and  the  cement  is  added  gradually,  being  made 
to  flow  through  the  neck  of  the  funnel  by  means  of  a  wire. 
While  the  cement  is  being  run  into  the  flask,  the  latter  should  be 
tapped  gently  against  the  table.  If  the  top  of  the  latter  is  of 
stone,  a  piece  of  blotting  paper  may  be  laid  over  this  to  pre- 
vent breakage.  When  all  the  cement  has  been  introduced  into 
the  flask,  the  reading  is  taken,  a  thermometer  is  again  placed  in 
the  oil,  and  the  temperature  again  observed.  By  the  use  of  the 


SPECIFIC    GRAVITY 


365 


corrections  and  table  given  below,  the  specific  gravity  may  be 
found  at  a  glance. 

TABLE  XXL— CORRECTIONS  FOR  CHANGES  IN  TEMPERATURE. 

For  a  rise  in  temperature  deduct  from  the  observed  reading  of  the 

specific  gravity  bottle,  for  a  decrease  add 


°c. 

CC. 

°C. 

CC. 

°C. 

CC. 

cc. 

CC. 

0.2 

0.02 

1.2 

0.13 

2.2 

0-34 

3-2 

0.35 

0.4 

0.04 

1-4 

0.15 

2.4 

O.26 

3-4 

o-37 

0.6 

O.O7 

1.6 

0.18 

2.6 

0.29 

3-6 

0.40 

0.8 

O.O9 

1.8 

O.2O 

2.8 

0.3I 

3-8 

0.42 

I.O 

O.I  I 

2.0 

O.22 

3-o 

0-33 

4.0 

0.44 

TABLE  XXII. — VALUES  OF  SPECIFIC  GRAVITY  IN  TERMS  OF  THE  READ- 
INGS OF  THE  LE  CHATEUER  APPARATUS,  WHEN  USING  64 
GRAMS  OF  CEMENT. 


CC. 

0.00 

O.O2 

0.04 

0.06 

o.oS 

19-50 

3.282 

3-279 

3-275 

3-272 

3-269 

0.60 

3-265 

3.262 

3-258 

3-255 

3.252 

0.70 

3-249 

3.246 

3.242 

3.239 

3.^36 

0.80 

3-232 

3.229 

3-225 

3.222 

3.219 

0.90 

3.216 

3-213 

3.209 

3.206 

3.203 

20.00 

3.200 

3-197 

3-194 

3.190 

3.187 

0.10 

3.184 

3.178 

3.174 

3.I7I 

O.2O 

3.168 

3-J65 

3.162 

3.159 

3.156 

0.30 

3-153 

3-J50 

3.147 

3-143 

3.140 

O.4O 

3.137 

3.134 

3-131 

3.128 

3-125 

0.50 
0.60 

3.122 

3-I07 

3-II9 
3-I04 

3.116 
3.101 

3-098 

3.IIO 
3.095 

O.7O 

3.092 

3.089 

3.086 

3-083 

3.080 

0.80 

3-077 

3-074 

3.071 

3.068 

3.065 

0.90 

3-063 

3-059 

3-056 

3-054 

3.05I 

21.00 

3.048 

3-045 

3.042 

3.039 

3.036 

O.IO 

3-033 

3-030 

3.027 

3.025 

3.022 

0.20 

3.019 

3.016 

3.013 

3.011 

3.008 

0.30 

3-o°5 

3.002 

3.000 

2.997 

2-995 

0.40 

2.992 

2.989 

2.986 

2.983 

2.980 

O.5O 

2.977 

2-974 

2.971 

2.969 

2.966 

O.6o 

2.963 

2.960 

2-957 

2-955 

2.952 

0.70 

2.949 

2.946 

2-944 

2.942 

2-939 

0.80 

2.936 

2-933 

2.930 

2.928 

2.925 

0.90 

2.922 

2.919 

2.917 

2.914 

2.912 

The  temperature  corrections  are  based  upon  the  fact  that  the 
coefficient  of  expansion  of  kerosene   is   1.009,  that  of  glass  is 


366  PORTLAND  CEMENT 

1.00025  and  the  difference  in  expansion,  is  0.000875.  Since  the 
bulb  of  the  flask  (to  the  lower  mark)  has  a  volume  of  130  cc., 
the  correction  for  every  degree  C.  difference  in  temperature  will 
amount  to  0.000875  X  130  or  o.n  cc.  Hence  for  every  degree 
rise  in  temperature  of  the  second  thermometer  reading  over  the 
first,  we  must  deduct  o.  1 1  cc.  from  the  observed  reading  on  the 
upper  stem  of  the  bottle  and  for  every  degree  drop  in  tem- 
perature we  must  add  o.n  cc.  Table  XXI  shows  the 
correction  to  be  added  or  subtracted  for  various  changes  in 
temperature. 

NOTE. 

All  apparatus  purchased  for  the  determination  of  specific 
gravity  should  be  tested  as  to  the  accuracy  of  the  graduation. 
Or  else  they  should  be  sent  to  the  U.  S.  Bureau  of  Standards  for 
this  purpose.  Or  the  maker  may  be  made  to  furnish  a  certifi- 
cate from  the  bureau  as  to  the  accuracy  of  the  apparatus. 
We  have  frequently  found  apparatus  which  gave  incorrect  re- 
sults owing  to  faulty  graduations.  If  the  tester  wishes  to  stand- 
ardize the  apparatus  himself,  it  must  first  be  well  cleaned.  This 
should  be  done,  if  the  apparatus  is  new,  by  washing  well  with 
water  and  then  allowing  a  mixture  of  potassium  bichromate, 
water  and  sulphuric  acid  to  stand  in  it  over  night.  After  wash- 
ing and  drying  it  is  calibrated. 

In  the  case  of  Le  Chatelier's  apparatus  this  is  done  by  filling 
the  apparatus  with  water  to  the  mark  on  the  stem  below  the 
bulb.  The  weight  is  then  taken  accurately.  Water  is  now 
added  to  fill  the  bulb  to  the  lowest  graduation  on  the  stem  above 
the  bulb.  The  weight  is  again  taken.  The  bulb  b  should  of 
course  hold  exactly  20  cc.  The  weight  of  water  corresponding 
to  this  is  shown  by  the  table  below.  In  calibrating  the  specific 
gravity  apparatus,  it  is  not  sufficient  to  presume  that  20  cc.  of 
water  will  weigh  20  grams.  The  following  table  must  be  used 
or  the  error  will  be  appreciable. 

The  graduation  of  the  stem  is  then  checked  by  filling  up  to 


SPECIFIC    GRAVITY 


36? 


TABLE  XXIII. — APPARENT  WEIGHT    OF   ONE  CUBIC  CENTIMETER  OF 

WATER  AT  DIFFERENT  TEMPERATURES  AS  WEIGHED  WITH  BRASS 

WEIGHTS  IN  AIR.    CORRECTED  FOR  THE  EXPANSION  OF  GLASS. 

H.  I,.  Payne.     Chemical  Engineer,  5,  237. 


Apparent  weight 

Apparent  weight 

Temper- 

Temper- 

ature 

ature 

°C. 

Standard  at 

Standard  at 

°C.  . 

Standard  at 

Standard  at 

15°  c. 

25°  C. 

15°  c. 

25°  C. 

15 

0.99806 

0.99783 

25 

0.99581 

0.99604 

16 

0.99789 

0.99770 

26 

0-99533 

0.99581 

17 

0.99770 

o  99756 

27 

0.99524 

0-99557 

18 

0.99751 

0.99741 

28 

0-99495 

3-99531 

19 

0.99729 

0.99724 

29 

0.99464 

0.99505 

20 

0.99706 

0.99707 

30 

0.99432 

0.99478 

21 

0.99684 

0.99689 

31 

0.99400 

0.99450 

22 

0.99660 

0.99669 

32 

0.99366 

0.99421 

23 

0.99640 

0.99648 

33 

0.99432 

0.99392 

24 

0.99608 

0.99627 

34 

o  99297 

0.99361 

25 

0.99581 

0.99604 

35 

0.99261 

0.99330 

the  upper  mark.  The  stem  should  hold  3  cc.  between  the  upper 
and  lower  graduations.  With  the  author's  improved  specific 
gravity  bottle,  the  bulb  should  hold  19.5  cc.  and  the  upper  stem 
between  the  graduations  3.5  cc.  Usually  the  error  with  the  Le 
Chatelier  apparatus  is  slight. 

With  the  Jackson  apparatus,  described  further  on,  the  bulb 
b  of  the  burette  should  hold  180  cc.  and  the  stem  5.70  cc.  The 
flask  should  hold  100  cc.  or  if  the  burette  bulb  holds  less  than 
1 80  cc.  the  flask  should  hold  the  contents  of  the  bulb  plus  20 
cc.  To  calibrate  the  burette  of  this  apparatus,  it  should  be 
cleaned  as  mentioned  above  and  filled  with  water.  The  contents 
of  the  bulb  are  first  run  into  an  ordinary  stoppered  flask  and  the 
weight  taken  and  then  the  contents  of  the  stem  added  in  two  or 
three  lots  so  as  to  check  the  graduation,  the  weight  being  taken 
after  each  reading.  The  flask  of  this  apparatus  should  always 
be  checked  by  running  in  the  contents  of  the  bulb  and  then 
taking  the  weight.  Water  is  then  added  to  fill  up  to  the  mark 
on  the  stopper  and  the  weight  again  taken.  The  difference  be- 
tween the  two  weights  should  be  equivalent  to  20  cc. 


368  PORTLAND  CEMENT 

OTHER  METHODS. 
With  the  Schumann-Candlot  Apparatus. 

Two  forms  of  apparatus  in  frequent  use,  particularly  abroad, 
for  taking  the  specific  gravity  of  cement  are  that  of  Schumann 
and  also  Candlots  modification  of  this.  To  the  author  neither 
of  these  have  any  points  of  superiority  over  Le  Chatelier's 


a 


Fig.  114. — Schumann's  apparatus  for  specific  gravity. 

apparatus.  Schumann's  original  form  of  specific  gravity  appara- 
tus is  shown  in  Fig.  114.  It  is  used  just  as  Le  Chatelier's,  100 
grams  of  cement  being  employed  and  the  flask  being  filled  with 
liquid  to  the  lowest  graduation  on  the  stem.  The  readings  on 
the  latter  are  obtained  in  cc.  and  the  elevation  of  the  liquid 


SPECIFIC    GRAVITY 


369 


caused  by  the  introduction  of  the  cement  gives  the  volume  dis- 
placed by  the  latter. 

The  Schumann-Candlot  apparatus  (Fig.  115)  consists  of  a 
graduated  tube,  B,  terminated  by  a  bulb,  A.  This  tube  fits  tightly 
on  the  flask,  D,  by  means  of  a  ground  joint.  To  use  the  apparatus, 
pararfine,  turpentine,  or  benzine  is  introduced  into  the  detached 
and  inverted  tube,  B,  in  sufficient  quantity  to  bring  the  level  of 


Fig.  115.— Schumaun-Candlot  apparatus  for  specific  gravity. 

the  liquid  above  the  zero  point  on  the  tube  when  the  latter  is  in 
position  on  the  flask,  D.  A  note  is  then  made  of  this  point,  the 
tube  is  inverted  and  the  flask  detached.  Into  the  latter  is  then 
introduced  a  known  weight  (usually  100  grams)  of  cement,  and 
the  flask  is  again  connected  with  the  tube.  The  whole  apparatus 
is  now  agitated  to  expel  air  bubbles,  then  set  in  an  upright  posi- 
tion and  the  new  height  to  which  the  liquid  rises  is  read.  The 
difference  between  this  height  and  the  last  is  the  volume  of  liquid 
displaced  by  the  cement.  To  find  the  specific  gravity  of  the  ce- 
ment divide  the  weight  of  cement  taken  by  the  volume  displaced, 
the  result  will  be  the  specific  gravity. 

Jackson's  Apparatus. 

Mr.  Daniel  D.  Jackson  has  devised  an  apparatus  for  the  deter- 
24 


370  PORTLAND  CEMENT 

niination  of   specific  gravity  which   is  shown  in  Fig.    116,   and 
which  he  describes  as  follows:1 


Fig.  116. — Jackson's  specific  gravity  apparatus. 

Above  is  suspended  a  burette  with  graduations  about  9  inches 
(23  cm.)  long,  and  with  an  inside  diameter  of  about  Y^  inch  (0.6 

i  Jour.  Soc.  Chem.  Ind.,  XXIII,  No.  11. 


SPECIFIC    GRAVITY  371 

cm.).  This  is  connected  with  a  glass  bulb  approximately  5^ 
inches  (13  cm.)  long  and  i^4  inch  (4.5  cm.)  in  diameter. 

The  Erlenmeyer  flask  below  is  of  heavy  glass  and  contains 
a  ground  glass  stopper,  which  is  hollow,  and  has  a  neck  of  the 
same  bore  as  the  burette.  The  flask  has  a  capacity  of  exactly  203 
cubic  centimeters  up  to  the  graduation  on  the  neck  of  the  stopper. 

In  order  that  the  work  may  be  more  rapid,  the  burette  is  not 
graduated  in  cubic  centimeters  as  in  other  instruments  of  this 
nature,  but  is  made  to  read  directly  in  specific  gravity.  The  manu- 
facturer of  the  instrument  (Emil  Greiner,  78  John  Street,  New 
York  City),  makes  the  glass  bulb  of  such  a  size  that  from  the 
mark  on  the  neck  at  the  top  to  the  mark  on  the  burette  just  be- 
low the  bulb,  the  capacity  is  exactly  180  cubic  centimeters.  If  50 
grams  of  cement  are  taken,  this  mark  represents  a  specific  gravity 
of  2.50. 

200  (capacity  of  flask). 
— 180  capacity  of  bulb  to  ist  graduation. 

=  20  volume  displaced  by  50  grams  of  cement. 
50  -T-  20  =  2.50,  specific  gravity. 

The  burette  is  graduated  for  every  0.05  in  specific  gravity  and 
five  equidistant  marks  are  placed  between  each  of  these  accurate 
graduations.  In  this  way  the  instrument  is  made  to  read  with 
accuracy  to  o.oi  in  specific  gravity. 

Method  of  Determination. — To  determine  the  specific  gravity 
of  a  cement  by  means  of  this  instrument: 

1.  Weigh  out  accurately  to  the  tenths'  place  of  decimals  50 
grams  of  the  dry  sample  of  cement. 

2.  Fill  the  bulb  and  burette  with  kerosene,  leaving  just  space 
enough  to  take  the  temperature  by  introducing  a  thermometer 
through  the  neck.     Remove  fhe  thermometer  and  add  sufficient 
kerosene  to  fill  exactly  to  the  mark  on  the  neck,  drawing  off  any 
excess  by  means  of  the  burette. 

3.  Run  into  the  unstoppered  Erlenmeyer  flask  about  one-half 
of  the  kerosene  in  the  bulb.    Then  pour  in  slowly  the  50  grams  of 
cement  and  revolve  to  remove  air  bubbles.     Run  in  more  kerosene 
until  any  adhering  cement  is  carefully  washed  from  the  neck  of 
the  flask,  and  the  kerosene  is  just  below  the  ground  glass. 


372 


PORTLAND  CEMENT 


TABLE  XXIV.— CORRECTION  IN  SPECIFIC  GRAVITY  IN  VARIOUS  PORTIONS 

OF  THE  GRADUATED  SCALE  DUE  TO  CHANGE  IN  TEMPERATURE, 

FAHRENHEIT,  DURING  THF  DETERMINATION. 

Read  the  temperature  of  the  oil  in  the  bulb  before  the  determination,  and 
of  the  oil  in  the  flask  after  the  determination.  Add  the  correction  if  the 
temperature  of  the  oil  increases,  and  subtract  if  it  decreases. 


Change  in 
temper- 
ature, Fah- 
renheit 

2.50 

to 

2.60 

2.6o 
to 

2.70 

2.70 
to 
2.80 

2.8o 

to 

2.90 

2.90 
to 

3-00 

3-00 
to 
3-10 

3-10 
to 
3.20 

3.20 

to 

3-30 

3-30 
to 
340 

3-40 
to 

350 

0-5° 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

1.0 

O.OI 

O.OI 

O.O2 

O.O2 

O.O2 

O.O2 

O.O2 

O.O2 

O.O2 

O.O2 

i-5 

O.O2 

O.O2 

O.O2 

O.O2 

0.03 

0.03 

0.03 

0.03 

0.03 

0.05 

2.0 

0.03 

0.03 

0.03 

0.03 

0.03 

O.O4 

O.O4 

O.O4 

0.04 

0.05 

2-5 

0.03 

0.04 

O.O4 

O.O4 

O.O4 

0.05 

0.05 

0.05 

O.o6 

O.O6 

3-0 

0.04 

0.04 

0.05 

0.05 

0.05 

0.05 

O.O6 

O.O6 

0.07 

O.O7 

3.5 

0.05 

0.05 

0.05 

O.O6 

O.O6 

0.06 

0.07 

0.07 

0.08 

0.08 

4.0 

0.05 

0.06 

O.O6 

O.O6 

O.O7 

0.07 

0.08 

0.08 

0.09 

0.09 

4.5 

0.06 

0.06 

0.07 

O.O7 

0.08 

0.08 

0.09 

0.09 

O.IO 

O.IO 

5-o 

0.07 

0.07 

0.08 

0.08 

0.09 

0.09 

O.IO 

O.IO 

O.I  I 

0.12 

5-5 

0.07 

0.08 

0.08 

0.09 

0.09 

O.IO 

O.IO 

O.  II 

O.I2 

0.13 

6.0 

0.08 

0.08 

0.09 

O.IO 

O.IO 

O.I  I 

O.I  I 

O.I2 

0.13 

0.14 

6.5 

0.08 

0.09 

O.IO 

O.IO 

O.I  I 

0,12 

O.I2 

0.13 

0.14 

0.15 

7.0 

0.09 

O.IO 

O.I  I 

O.I  I 

O.I2 

0.13 

0.13 

0.14 

0.15 

0.16 

7-5 

O.IO 

O.I  I 

O.I  I 

0.12 

0.13 

0.14 

0.14 

O.I5 

0.17 

0.17 

8.0 

O.IO 

O.I  I 

0.12 

0.13 

O.I4 

0.14 

O.I5 

0.16 

0.18 

0.18 

8-5 

O.I  I 

0.12 

0.13 

0.14 

0.14 

0.15 

0.16 

0.17 

0.19 

0.20 

9.0 

O.I  I 

0.13 

0.14 

0.14 

0.15 

O.l6 

0.17 

0.18 

0.20 

0.21 

9-5 

0.12 

0.13 

0.14 

0.15 

0.16 

0.17 

0.18 

0.19 

0.21 

O.22 

IO.O 

O.I3 

0.14 

0.15 

0.16 

0.17 

0.18 

0.19 

0.20 

O.22 

0.23 

4.  Use  a  little  glycerine  on  the  ground  part  of  the  funnel 
shaped   stopper   and   place   this   in  position   and   turn   it  to   fit 
tightly.     Run  in  kerosene  exactly  to  the  200  cubic  centimeter 
graduation  on  the  neck,  making  sure  that  no  air  bubbles  remain 
in  the  flask. 

5.  Read  the  specific  gravity  from  the  graduation  on  the  burette 
and  then  the  temperature  of  the  oil  in  the  flask,  noting  the  differ- 
ence between  the  temperature  of  the  oil  in  the  bulb  before  the  de- 
termination and  the  temperature  of  the  oil  in  the  flask  after  the 
determination. 

Make  a  temperature  correction  to  the  reading  of  the  specific 
gravity  by  the  use  of  the  accompanying  tables.  (Tables  XXIV 
and  XXV.) 


SPECIFIC    GRAVITY 


373 


TABLE  XXV. —CORRECTION  IN  SPECIFIC  GRAVITY  IN  VARIOUS  PORTIONS 

OF  THE  GRADUATED  SCALE  DUE  TO  CHANGE  IN  TEMPERATURE, 

CENTIGRADE,  DURING  THE  DETERMINATION. 

Read  the  temperature  of  the  oil  in  the  bulb  before  the  determination  and 
of  the  oil  in  the  flask  after  the  determination.  Add  the  correction  if  the 
temperature  of  the  oil  increases,  and  subtract  it  if  it  decreases. 


Change  in 
tempera- 
ture, cen- 
tigrade 

2.50 
to 

2.60 

2.6o 
to 

2.70 

2.70 
to 
2.80 

2.80 
to 

2.90 

2.90 
to 
3-oo 

3-00 
to 

3.10 

3-io 
to 

3-20 

3-20 

to 
3-3° 

3-30 
to 

3-40 

3.40 
to 

350 

0.2° 

0.00 

0.01 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

0.4 

0.01 

0.01 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

O.O2 

O.O2 

0.6 

0.01 

0.02 

O.O2 

O.O2 

O.O2 

O.O2 

0.02 

O.O2 

O.O2 

O.O2 

0.8 

O.O2 

O.O2 

0.02 

O.O2 

O.O2 

0.03 

0.03 

0.03 

0.03 

0.03 

.0 

O.O2 

0.03 

0.03 

0.03 

0.03 

0.03 

0.03 

O.O4 

0.04 

0.04 

.2 

0.03 

0.03 

0.03 

0.03 

0.04 

0.04 

O.O4 

O.O4 

0.05 

0.05 

•4 

0.03 

O.O4 

O.O4 

O.O4 

O.O4 

0.05 

0.05 

0.05 

O.o6 

O.O6 

.6 

0.04 

O.O4 

O.O4 

0.05 

0.05 

0.05 

0.05 

0.06 

O.o6 

O.O7 

.8 

0.04 

0.05 

0.05 

0.05 

O.o6 

O.o6 

O.o6 

0.06 

O.O7 

0.07 

2.0 

0.05 

0.05 

0.05 

O.o6 

O.O6 

O.O6 

0.07 

0.07 

0.08 

0.08 

2.2 

0.05 

O.o6 

0.06 

O.O6 

O.O7 

0.07 

0.08 

0.08 

0.09 

0.09 

2.4 

O.o6 

O.o6 

0.06 

0.07 

O.O7 

0.08 

0.08 

0.09 

O.IO 

O.IO 

2.6 

O.o6 

O.O7 

O.O7 

0.07 

0.08 

0.08 

0.09 

0.09 

O.IO 

O.II 

2.8 

O.OJ 

O.O7 

O.o8 

0.08 

0.09 

0.09 

O.IO 

O.IO 

O.II 

0.12 

'  3.0 

0.07 

0.08 

0.08 

0.09 

0.09 

O.IO 

O.IO 

O.II 

0.12 

0.12 

3-2 

0.07 

0.08 

0.09 

0.09 

O.IO 

O.IO 

O.II 

0.12 

0.13 

0.13 

3-4 

O.o8 

0.09 

0.09 

O.IO 

O.IO 

O.II 

0.12 

0.12 

0.13 

0.14 

3-6 

0.08 

0.09 

O.IO 

O.IO 

O.II 

O.I2 

0.12 

0.13 

0.14 

0.15 

3-8 

0.09 

O.IO 

O.IO 

O.II 

0.12 

0.12 

0.13 

0.14 

0.15 

0.16 

4-0 

O.O9 

O.IO 

O.I  I 

0.12 

0.12 

0.13 

0.14 

O.I4 

0.16 

0.17 

4-2 

O.IO 

O.I  I 

O.II 

0.12 

0.13 

0.14 

0.14 

0.15 

0.17 

0.17 

4.4 

O.IO 

O.I  I 

O.I2 

0.13 

0.13 

0.14 

0.15 

0.16 

0.17 

0.18 

4-6 

O.I  I 

0.12 

O.I2 

0.13 

0.14 

0.15 

0.16 

0.17 

0.18 

0.19 

4-8 

O.I  I 

0.12 

O.I3 

O.I4 

0.15 

0.15 

o.  16 

0.17 

0.19 

O.20 

5.o 

0.12 

O.I3 

0.14 

0.14 

0.15 

0.16 

0.17 

0.18 

O.2O 

0.21 

For  the  convenience  of  those  using  the  Centigrade  thermom- 
eter the  table  of  corrections  for  that  instrument  has  also  been 
compiled. 

It  is  thought  possible  that  the  variation  in  the  different  brands 
of  kerosene  might  be  sufficient  to  cause  an  error  in  the  determina- 
tion. A  collection  of  various  good  and  bad  kerosenes  was  made 
and  the  coefficient  of  expansion  of  each  sample  was  determined. 

The  differences  in  expansion  found  were  entirely  within  the 
limit  of  error  of  the  determination. 


374 


PORTLAND  CEMENT 


With  the  instrument  herein  described  the  time  required  to 
make  a  determination  is  about  ten  minutes,  and  the  accuracy  is 
to  o.oi. 

Simple  Apparatus  for  Specific  Gravity. 

Fig.  117  shows  a  simple  form  of  apparatus  which  the  writer  has 
usually  used  for  taking  specific  gravity.  It  is,  of  course,  not  so 
neat  and  elegant  as  the  apparatus  devised  by  Mr.  Jackson,  but  it 


Fig.  117.— NSimple  apparatus  for  specific  gravity. 

can  be  made  of  apparatus  found  about  the  laboratory  or  which 
can  be  purchased  from  the  stock  of  any  dealer.  Referring  to  the 
illustration  it  will  be  seen  that  in  place  of  the  special  form  of  bu- 
rette used  in  the  Jackson  apparatus,  a  50  cc.  automatic  pipette 
and  a  25  cc.  burette  graduated  in  1/20  cc.  and  which  can  be 


SPECIFIC    GRAVITY  375 

read  to  1/40  cc.  are  used.  These  are  mounted  on  a  stand  and 
connected  with  a  reservoir  of  kerosene  on  a  shelf  above.  In 
place  of  the  special  flask  of  the  Jackson  apparatus  a  test-tube 
drawn  out  near  its  upper  end  to  about  54  or  %-inch  in  diameter 
is  used.  The  test-tube  should  be  about  8  inches  long  and  I  inch 
in  diameter,  and  should  hold  about  100  cc.  It  is  then  drawn  out 
about  6  inches  from  the  bottom  and  a  mark  made  on  the  neck  by 
covering  the  latter  with  wax,  scraping  this  away,  in  a  ring 
around  the  drawn  out  part,  and  then  moistening  this  with  hydro- 
fluoric acid.  Holes  about  il/2  inches  deep  and  just  large  enough 
to  hold  the  tube  are  then  bored  in  the  board,  to  form  a  stand  for 
the  test-tube. 

To  determine  the  specific  gravity  of  a  cement,  dry  the  tube  and 
run  in  a  pipette  full  of  kerosene.  Then  fill  from  the  burette  to 
the  mark.  This  will  require  about  75  cc.  or  possibly  more.  Now 
note  the  quantity  and  dry  the  flask.  Again  run  in  a  pipette  full' 
of  kerosene,  placing  the  opening  of  the  pipette  well  down  in  the 
tube  so  as  not  to  wet  the  neck  of  the  latter.  Now  brush  into  the 
flask  25  grams  of  the  cement  to  be  tested,  after  carefully  weigh- 
ing the  latter  to  at  least  0.025  gram.  The  cement  should  be 
brushed  into  the  flask  very  gradually  and  any  particles  adhering 
to  the  upper  part  of  the  tube  brushed  into  the  neck.  Now  add 
kerosene  carefully  from  the  pipette  until  the  mark  on  the  neck 
is  reached.  The  volume  displaced  is  the  difference  between  this 
quantity  and  that  required  to  fill  the  empty  tube;  and  the  specific 
gravity  is  the  weight  in  grams,  or  25,  divided  by  the  volume  dis- 
placed. For  example,  if  it  takes  81.35  cc.  to  fill  the  flask  to  the 
mark  when  empty  and  it  takes  73.3  to  fill  it  with*  the  cement,  the 
specific  gravity  of  the  latter  will  be  25  -f-  (81.35 — 73-3)  or 
25 -=-8.05 =3.1 1.  A  large  number  of  the  tubes  can  be  made  and 
the  volume  required  to  fill  each  etched  on  with  hydrofluoric  acid. 
A  dry  tube  will  then  always  be  ready.  The  cement  sample  should 
be  weighed  out  and  allowed  to  stand  15  minutes,  on  the  shelf  by 
the  large  bottle  of  kerosene.  This  avoids  the  necessity  of  making 
corrections  for  temperature.  A  table  showing  the  specific  grav- 
ity corresponding  to  any  displacement  is  given  below : 


376 


PORTLAND  CEMENT 


TABLE  XXVI.— SHOWING  CONNECTION  BETWEEN  DISPLACEMENT 
CAUSED  BY  25  GRAMS  OF  CEMENT  AND  SPECIFIC  GRAVITY. 


Displacement 
cc. 

Specific  gravity 

Displacement 
cc. 

Specific  gravity 

7.500 

3-33 

8.000 

3-13 

7-525 

3-32 

8.025 

3.12 

7-550 

3-31 

8.050 

3-II 

7-575 

3-30 

8.075 

3.10 

7.600 

3.29 

8.100 

3-09 

7.625 

328 

8.125 

3.08 

7.650 

3-27 

8.150 

3-07 

7-675 

3-26 

8.175 

306 

7.700 

3-25 

8.200 

3.05 

7-725 

3-24 

8.225 

3-04 

7-750 

3-23 

8.250 

3-03 

7-775 

3.22 

8.275 

302 

7.800 

3.21 

8.300 

3.01 

7-825 

3-20 

8.325 

3.00 

7.850 

3.19 

8.350 

2.99 

7.875 

3.17 

8.375 

298 

7.900 

3.16 

8.400 

2.98 

7.925 

3.15 

8.425 

2.97 

7-950 

3-14 

8.450 

2.96 

7-975 

3-13 

8.475 

2-95 

The  apparatus  must  be  set  in  a  place  free  from  sudden  changes 
of  temperature,  and  the  measuring  must  be  carefully  done.  The 
arrangement  is  well  adapted  for  use  where  only  a  few  determina- 
tions are  made  each  day. 

Meade's  Suspension  Method. 

For  very  accurately  determining  the  specific  gravity  of  Port- 
land cement,  the  author  has  used  to  some  extent  the  following 
method:  It  will  also  be  found  useful  if  special  apparatus  is  not 
at  hand  or  where  the  specific  gravity  of  a  small  quantity  of  ce- 
ment is  desired.  In  this  latter  connection,  the  writer  has  found 
it  especially  applicable  for  ignited  samples  of  cement,  as  the 
appliances  at  hand  in  the  ordinary  cement  testing  laboratory  are 
not  sufficient  to  allow  of  more  than  5  or  10  grams  of  cement 
being  ignited  at  a  low  red  heat  at  one  time  and  none  of  the  usual 
forms  of  apparatus  used  for  taking  the  specific  gravity  of  cement 
are  suited  to  the  employment  of  such  a  small  sample.  The  meth- 
od follows: 


SPECIFIC    GRAVITY 


377 


From  one  arm,  a  (the  left),  of  the  balance  take  off  the  balance 
pan  and  in  its  place  suspend  from  the  stirrup,  as  shown  in  Fig. 
1 1 8,  a  50  gram  weight,  b  (or  any  weight  sufficient  to  more  than 
balance  this  pan  such  as  a  lead  fishing  sinker).  Take  the  weight 
of  this  on  the  other  pan  and  call  this  weight  "A."  Now  attach 
to  this  a  fine  silk  thread  or  wire  a  50  or  100  cc.  pycnometer,  c 
(a  small  100  cc.  Erlenmeyer  flask  with  a  narrow  mouth  will  also 
do).  Weigh  the  pycnometer  so  suspended  and  call  the  total 


T 


Fig.  118.— Suspension  method  for  taking  specific  gravity  of  Portland  cement. 

weight  "B."  B — A  will  then  be  the  weight  of  the  pycnometer  in 
air.  Now  fill  the  pycnometer  with  water  in  the  usual  way  care- 
fully forcing  out  all  air  and  weigh  suspended  in  a  tall  narrow 
beaker  or  jar,  d,  of  water.  Call  this  weight  "C."  "Loss  in 
water"  =  (B— A)— (C— A)  —  B— C.  Now  dry  the  pycnom- 
eter, fill  with  oil  and  weigh  suspended  in  kerosene.  Call  this 
weight  "D."  "Loss  in  kerosene"  —  (B— A)— (D— A)  =  B— D. 

.  '  'Loss  in  kerosene* ' 

Specific  gravity  of  the  kerosene  —  -^T • ~  >~- 

Loss  in  water' 


PORTLAND  CEMKNT 

Now  remove  the  pycnometer  and  pour  out  half  of  the  kerosene, 
introduce  W  (usually  5  to  10)  grams  of  the  ignited  cement  and 
mix  thoroughly  by  twirling  around  the  contents  of  the  pycnom- 
eter. Fill  the  pycnometer  to  the  neck  with  oil  and  allow  a  few 
minutes  for  the  contents  to  settle.  Fill  the  neck  full  by  pour- 
ing down  the  sides,  suspend  in  kerosene  and  weigh  as  before. 
Call  weight  "E." 

0       ..c  r  ,  W  X  specific  gravity  of  the  oil 

Specific  gravity  of  the  cement  — r.-T7    ,    _x — £-= . 

( W  -f-  L))  —  h, 

The  temperature  of  the  oil  should  not  change  more  than  2°  C. 
during  the  time  between  the  taking  of  its  own  density  and  that 
of  the  cement.  The  weight  of  the  pycnometer  suspended  in 
water  need  be  taken  but  once.  After  this  is  done  a  determination 
can  be  easily  made  in  ten  minutes.  Even  the  finest  particles  of 
the  cement  settle  in  a  few  minutes  and  results  obtained  by  the 
method  are  very  trustworthy. 

An  example  of  the  calculation  is  given  below : — 

Weight  to  balance   (A)    11.823 

Weight   of   pycnometer   suspended   to   the 

above  in  air   (B)    40.825 

Weight   of   pycnometer   suspended   to   the 

above  in  water   (C)    29.181 

"Loss    in    water"    =     (B— A)  (C— A)     =     (40.825— 

11.823)  —  (29.181  —  11.823)  =  11.644. 

(The   above   are   permanent    results   and   provided   the   same 
pycnometer  or  flask  is  used  for  each  determination  need  be  ob 
tained  but  once.) 

Weight   of   pycnometer   suspended   in   kerosene    (D)    31.662. 
"Loss  in  oil"  =  (B  — A)  —  (D  — A)  =  (40.825  —  11.823)  — 
(31.662—11.823)   =  9.163. 

0       ._  **."•-*    -1  LOSS  in  oil  9.163 

Specific  gravity  of  oil  = : —         -  =  — — 0.7-57. 

Loss  in  water          11.644 

Weight   of    pycnometer    +    IO   grams   of    cement    suspended 
in   kerosene    (E)    39-T52 


SPECIFIC    GRAVITY  379 

...  W  X  sp.  gravity  of  oil 

Specific  gravity  of  cement  =  (W  +  D)  —  E 

10  X  0.787  7-87  6 


(  10  +  31.662)  —  39.152  2.510 

Another  method  for  taking  the  specific  gravity  by  means  of 
the  pycnometer  is  as  follows: 

First  weigh  the  bottle,  empty,  then  fill  the  bottle  with  water 
and  weigh.  Then  dry  and  fill  with  benzine  and  weigh.  Calcu- 
late the  specific  gravity  of  benzine  from  the  formula 


W—  p1 

where  .r=sp.  gr.  of  benzine,  B=  weight  of  bottle  full  of  ben- 
zine, W=  weight  of  bottle  full  of  water,  and  p=  weight  of  the 
empty  bottle. 

Now  introduce  a  weighed  portion  of  the  cement  into  the 
bottle,  fill  with  benzine,  and  weigh.  The  specific  gravity  of  the 
cement  may  then  be  found  by  the  formula 

C  X  x 
B  +  C  —  D' 

where  B=  weight  of  the  bottle  full  of  benzine,  C—  weight  of 
the  cement.  D  =  weight  of  the  bottle  and  the  cement  and  the 
benzine,  .r=specific  gravity  of  the  cement  as  found  above,  and 
X=  specific  gravity  of  the  cement.  Turpentine  or  paraffin  may 
be  used  in  place  of  benzine. 

OBSERVATIONS   ON  SPECIFIC   GRAVITY. 
Effect  of  Burning  on  the  Specific  Gravity  of  Cement. 

While  a  minimum  specific  gravity  clause  is  a  feature  of  every 
specification  for  Portland  cement,  there  is  probably  no  test 
which  taken  by  itself  might  lead  to  more  faulty  conclusions. 

Originally  in  the  Standard  Specifications  for  cement  under 
the  heading  "General  Observations,"  appeared  the  following 
paragraph  : 


380  .  PORTLAND  CEMENT 

"Specific  Gravity  is  useful  in  detecting  adulteration  and  under- 
burning.  The  results  of  tests  of  specific  gravity  are  not  neces^ 
sarily  conclusive  as  an  indication  of  the  quality  of  a  cement,  but 
when  in  combination  with  the  results  of  other  tests  may  afford 
valuable  indications." 

Shortly  after  the  publication  of  this  report  the  writer  began 
a  series  of  experiments  in  connection  with  one  of  his  assistants, 
Mr.  L.  C.  Hawk,  to  determine  the  causes  which  tend  to  lower 
the  specific  gravity  of  Portland  cement  and  the  actual  value  of 
the  test.  The  Committee  on  Technical  Research  of  the  Associa- 
tion of  American  Cement  Manufacturers  took  up  the  subject  and 
their  two  reports  will  be  found  in  the  proceedings  of  this  associa- 
tion. Butler,  an  English  chemist,  also  made  experiments  along 
the  same  line  which  he  described  in  the  proceedings  of  the 
Institute  of  Civil  Engineers. 

Naturally  the  first  condition  to  receive  attention  was  the  de- 
gree of  burning.  This  was  done  in  the  following  manner:  A 
kiln  was  detected  turning  out  under-burned  clinker,  and  from 
this  kiln  twelve  samples  were  drawn  as  the  kiln  was  heated  up  to 
slightly  above  normal  temperature.  From  these  samples,  four 
were  selected  as  representing  ( i )  very  soft  under-burned  clinker, 
(2)  slightly  under-burned  clinker,  (3)  normally  burned  clinker 
and  (4)  very  hard  burned  clinker.  These  clinkers  were  then 
ground  as  rapidly  as  possible  to  pass  a  standard  loo-mesh  sieve 
and  the  specific  gravity  at  once  taken.  The  need  of  haste  was 
occasioned  by  the  fact  that  under-burned  clinker  rapidly  absorbs 
carbon  dioxide  and  water  from  the  air,  which  lowers  its  specific 
gravity.  The  specific  gravity  of  the  three  samples  was  found 
to  be: 

1.  Very  soft  under-burned  clinker 3.208 

2.  Slightly  under-burned  clinker   3.222 

3.  Normally  burned  clinker   3-214 

4.  Very  hard  burned  clinker 3-234 

The  ground  clinker  was  also  mixed  with  2  per  cent,  plaster 
of  Paris,  and  made  into  pats  which  were  subjected  to  the  steam 
test.  At  the  end  of  two  hours  the  pat  made  from  the  very  soft 


SPECIFIC    GRAVITY  381 

under-burned  clinker  had  entirely  disintegrated.  At  the  end  of 
five  hours  the  pat  from  the  slightly  under-burned  clinker  had  be- 
come checked  and  partially  disintegrated.  The  other  two  pats 
not  only  stood  the  steam  test  satisfactorily,  but  five  hours  longer 
in  boiling  water  had  no  effect  upon  them.  Thus  we  see  that  al- 
though the  difference  in  specific  gravity  is  only  0.026  the  degree 
of  burning  in  the  four  samples  was  markedly  different. 

We  have  frequently  taken  the  specific  gravity  of  under-burned 
clinker  and  in  no  case  have  we  ever  found  it  below  that  of  the 
standard  specifications. 

The  experiments  made  by  the  members  of  the  Association  of 
American  Cement  Manufacturers  conducted  at  six  different  mills, 
gave  an  average  of  3.14  for  the  specific  gravity  of  the  under- 
burned  cements  and  3.18  for  that  of  the  hard  burned  ones. 

Effect   of  Adulteration   on   the  Specific   Gravity. 

The  effect  of  adulteration  can  of  course  be  calculated  accurate- 
ly. The  substances  most  available  for  adulteration  of  Portland 
cements  in  this  country  are  natural  cement,  raw  material  or 
limestone  and  slag.  Rosendale  or  natural  cement  has  probably 
been  used  more  than  any  of  the  others.  Its  specific  gravity 
ranges  between  2.8  and  3.1.  In  detecting  a  mixture  of  Rosen- 
dale  cement  and  Portland  cement  the  value  of  the  test  will  de- 
pend entirely  upon  the  specific  gravity  of  the  Rosendale.  In 
the  case  of  a  natural  cement  with  a  specific  gravity  of  2.9  it 
would,  of  course,  be  possible  to  mix  as  much  as  i  part  Rosendale 
to  2  parts  Portland,  while  with  natural  cements  of  higher  density 
more  Rosendale  could  be  used. 

The  raw  material  or  cement-rock  of  the  Lehigh  district  has  a 
specific  gravity  of  about  2.7,  hence  very  little  of  it  could  be  used 
without  lowering  the  specific  gravity  appreciably.  Its  dark  color 
would  also  cause  its  presence  to  be  suspected  and  chemical 
analysis  would  readily  detect  it.  Limestones  average  in  specific 
gravity  about  2.8,  so  that  only  about  20  per  cent,  of  the  mix- 
ture could  be  used  without  lowering  the  specific  gravity  be- 
low that  called  for  by  the  standard  specifications.  In  the  case 


PORTLAND  CEMENT 


of  blast  furnace  slag,  the  density  of  which  is  somewhere  around 
3.0  large  quantities  could  be  used  without  detection  by  the 
specific  gravity  test.  The  writers  recently  had  a  sample  of  basic 
slag  containing  36  per  cent,  silica,  of  which  the  specific  gravity 
was  3.05.  A  mixture  of  I  part  of  this  slag  and  I  part  of  Port- 
land had  a  density  of  3.12. 

It  would  seem  therefore  that  while  the  test  would  be  of  value 
in  detecting  additions  of  limestone  or  cement-rock,  it  is  by  no 
means  an  infallible  one  or  even  a  reliable  one  for  detecting  ad- 
mixture of  Rosendale  or  slag. 

Effect  of  Seasoning  Cement  or  Clinker  on  Specific  Gravity. 
It  has  long  been  known  that  the  storage  of  cement  causes  a 
lowering  of  its  specific  gravity.  This  i-s  easily  explained  by  the 
fact  that  cements  on  exposure  to  air  absorb  carbon  dioxide  and 
water,  forming  calcium  carbonate  and  calcium  hydroxide.  The 
former  has  a  density  of  2.70  and  the  latter  of  2.08.  The  effect 
of  storage  on  cement  is  shown  by  the  following: 

TABLE  XXVII.— EFFECT  OF  SEASONING  ON  SPECIFIC 
GRAVITY  OF  CEMENT. 


Spe 

;ific  gra1 

irity 

Sample  No  

i 

2 

-? 

4 

c 

\Vhen  made  

3   TO 

32T 

T.    ifi 

•  *y 

3T  T 

.^1 

3T2 

o-  I0 

•  'o 

.20 

1  08 

5 

i  16 

.12 

•*  18 

.10 

3-TA 

o-uy 

3.0O 

O-1" 

•a  08 

O'io 

••*«* 

i  r>S 

•  M 

.14 

After  6  months  dried  at  100°  C 

3.00 

.04 

3.00 

3  °3 

3-°4 

•'3 

->  18 

•°9 

.12 

7      T» 

3-°9 

3-°9 

3.10 

.21 

3.10 

•*5 

3-J9 

Reference  to  the  above  table  shows  that  samples  2,  4  and  5 
would  have  failed  to  come  up  to  the  standard  specific  gravity 
specifications  after  six  months,  and  yet,  briquettes  made  of  the 
samples  at  the  same  time  the  specific  gravity  determinations  were 
made,  showed  the  cement  to  be  at  its  best,  after  storage  for  that 
length  of  time. 

A  sample  of  cement  had  a  specific  gravity  of  3.21  when  fresh 
and  after  lying  in  a  warehouse  three  years  had  a  specific  gravity 


SPECIFIC    GRAVITY  383 

of  only  3.02.  Its  properties  at  the  end  of  that  period  were 
excellent  and  the  only  noticeable  change  in  its  condition  was  that 
it  was  slightly  caked. 

It  is  now  generally  conceded  that  the  seasoning  of  cement 
is  an  advantage,  and  many  tests  by  various  operators  show  that 
cement  gives  its  best  strength  after  a  storage  of  from  three  to 
six  months.  Yet  it  is  probable  that  cement  which  has  been 
stored  this  length  of  time  will  have  a  specific  gravity  of  less 
than  3.10.  If  the  cement  does  not  absorb  some  carbon  dioxide 
and  water  no  benefits  will  be  derived  from  seasoning,  and  if  it 
does  absorb  them  the  specific  gravity  is  bound  to  be  lowered 
thereby.  The  absorption  of  3  per  cent,  carbon  dioxide  and  water 
is  sufficient  to  lower  the  specific  gravity  of  cement  below  3.10. 
An  under-burned  cement  which  failed  when  freshly  made  to 
stand  a  five  hours'  steam  test  without  complete  disintegration  had 
a  specific  gravity  of  3.185.  After  being  seasoned  one  month  it 
stood  five  hours'  steam  and  boiling  tests  perfectly,  but  its  specific 
gravity  had  fallen  to  only  3.082. 

Similarly  it  has  been  found,  however,  that  seasoned  clinker 
made  a  cement  of  lower  specific  gravity  than  would  have  been 
the  case  if  the  clinker  had  been  ground  fresh  from  the  kilns. 
Otherwise  the  cement  is  excellent.  For  example,  a  sample  of 
clinker  fresh  from  the  coolers  gave  a  specific  gravity  of  3.18: 
after  being  exposed  out  of  doors  for  one  month  the  specific 
gravity  fell  to  3.04,  and  after  two  months'  exposure  to  2.96.  The 
cement  made  from  the  exposed  clinker  had  neat  strength  of  677 
pounds  at  the  end  of  seven  days  and  765  pounds  at  the  end  of 
twenty-eight  days,  and  a  sand  strength  of  330  pounds  in  seven 
days  and  394  pounds  in  twenty-eight  days. 

It  will  be  seen  therefore  that  seasoning  or  storage  of  the  ce- 
ment has  a  much  greater  effect  upon  the  specific  gravity  than 
under-burning  or  adulteration. 

Specific  Gravity  Upon  Dried  and  Ignited  Samples. 
If  a  sample  which  has  been  kept  for  some  time  is  dried  at 
100°  C.,  its  specific  gravity  will  be  found  to  be  higher  than  it  was 
in  the  undried  condition,  (Refer  to  table  XXVII),  but  still  not  as 


PORTLAND  CE)MKNT 

high  as  when  it  was  freshly  made.  If  this  sample  is  subjected 
to  a  strong  ignition  in  a  platinum  crucible  over  a  good  blast  lamp, 
its  specific  gravity  will  still  further  increase  and  may  even  be 
more  than  the  original  specific  gravity  of  the  freshly  made  ce- 
ment. 

The  new  specifications  propose  in  cases  where  the  specific 
gravity  of  cement  falls  below  the  limit  prescribed  by  the  specifica- 
tions that  the  sample  should  be  ignited  and  the  specific  gravity  of 
the  ignited  sample  taken.  We  have  made  a  large  number  of  de- 
terminations of  specific  gravity  upon  seasoned  cements  from 
which  we  find  that  practically  all  samples  of  cement  when  ignited 
give  a  specific  gravity  of  between  3.15  and  3.22  and  that  most 
of  them  give  around  3.20.  This  conclusion  was  also  reached  by 
the  Committee  on  Technical  Research  of  the  Association  of 
American  Portland  Cement  Manufacturers^  and  by  Butler. 

Upon  igniting  a  mixture  of  40  per  cent.  Rosendale  and  60 
per  cent.  Portland  cement  having  a  specific  gravity  of  2.985  be- 
fore ignition  we  were  surprised  to  obtain  a  specific  gravity  of 
3.20.  This  result  was  checked  with  practically  the  same  result. 
A  mixture  of  40  per  cent,  cement-rock  and  60  per  cent.  Portland 
cement  which  had  a  specific  gravity  of  2.95,  gave  after  ignition 
3.20.  This  would  prove  that  the  ignition  of  the  cement  and  de- 
termination of  the  specific  gravity  of  the  ignited  sample  fails 
to  give  any  indication  of  adulteration  even  where  this  has  taken 
place  to  a  considerable  extent. 

The  new  requirement,  that  cement  which  falls  below  a  specific 
gravity  of  3.10  shall  also  not  show  more  than  4  per  cent,  loss  on 
ignition,  will  serve  to  detect  additions  of  limestone  but  will  not  of 
slag  or  Rosendale  cement,  since  these  substances  themselves 
show  very  small  loss  on  ignition.  Seasoning  will  also  cause  high 
loss  on  ignition  and  a  well-seasoned  cement  or  one  made  from 
seasoned  clinker  might  easily  show  a  loss  on  ignition  of  more 
than  4  per  cent.  If  this  loss  on  ignition  is  a  good  part  of  it 
water,  the  inspector  may  safely  conclude  that  no  adulteration  has 
been  practiced. 

In  conclusion  it  may  be  said  that  the  specific  gravity  determina- 


SPECIFIC    GRAVITY  385 

tion  is  of  little  value  in  determining  whether  cement  has  been 
under-burned  or  not.  The  experienced  cement  chemist  at  the 
mill  can  see  at  a  glance  by  looking  at  the  clinker  if  it  is  under- 
burned,  and  the  engineer  or  inspector  can  judge  better  by  the 
test  for  soundness.  It  is  also  for  the  reasons  given  above,  no 
indication  of  adulteration.  If,  however,  the  specific  gravity  of  a 
cement  is  low,  it  is  well  to  examine  it  a  little  more  closely,  to" 
see  if  it  is  adulterated,  by  the  methods  outlined  in  Chapter 
XIX,  on  "Detection  of  Adulteration." 


Chapter  XV. 


FINENESS. 


STANDARD  SPECIFICATION  AND  METHOD  OF  TEST. 


Specification. — It  shall  leave  by  weight  a  residue  of  not  more 
than  8  per  cent,  on  the  No.  100,  and  not  more  than  25  per  cent, 
on  the  No.  200  sieve. 

Method  of  Operating  the  Test. — Apparatus. — The  sieves  should 
be  circular,  about  20  cm.  (7.87  ins.)  in  diameter,  6  cm.  (2.36  ins.) 
high,  and  provided  with  a  pan  5  cm.  (1.97  ins.)  deep,  and  a 
cover. 

The  wire  cloth  should  be  woven  (not  twilled)  from  brass  wire 
having  the  following  diameters : 

No.  100,  0.0045  m-  J  No.  200,  0.0024  in. 

This  cloth  should  be  mounted  on  the  frames  without  distortion : 
the  mesh  should  be  regular  in  spacing  and  be  within  the  follow- 
ing limits: 

No.  loo,  96  to  too  meshes  to  the  linear  inch. 

No.  200,  1 88  to  200  meshes  to  the  linear  inch. 

Fifty  gram.  (1.76  oz.)  or  100  gr.  (3.52  oz.)  should  be  used  for 
the  test,  and  dried  at  a  temperature  of  100°  C.  (212°  F.)  prior  to 
sieving. 

Method. — The  thoroughly  dried  and  coarsely  screened  sample 
is  weighed  and  placed  on  the  No.  200  sieve,  which,  with  pan  and 
cover  attached,  is  held  in  one  hand  in  a  slightly  inclined  position, 
and  moved  forward  and  backward,  at  the  same  time  striking  the 
side  gently  with  the  palm  of  the  other  hand,  at  the  rate  of  about 
200  strokes  per  minute.  The  operation  is  continued  until  not 
more  than  one-tenth  of  I  per  cent,  passes  through  after  one  min- 
ute of  continuous  sieving.  The  residue  is  weighed,  then  placed 
on  the  No.  100  sieve  and  the  operation  repeated.  The  work  may 


FINENESS  387 

be  expedited  by  placing  in  the  sieve  a  small  quantity  of  large 
steel  shot.  The  results  should  be  reported  to  the  nearest  tenth 
of  i  per  cent. 

NOTES. 
Errors  in  Sieves. 

In  purchasing  sieves  for  making  the  fineness  test,  care  must  be 
exercised  to  see  that  they  are  within  the  limits  prescribed  by  the 
standard  rules,  for  there  are  many  so-called  standard  sieves  on 
the  market  which  are  anything  but  standard.  I  have  seen  a  No. 
100  test  sieve  bearing  the  name  of  a  well-known  firm,  which 
makes  a  specialty  of  supplying  apparatus  for  cement  testing, 
that  was  made  of  wire  cloth  containing,  to  the  linear  inch,  90 
meshes  one  way  by  93  the  other.  Not  only  may  standard  sieves 
not  contain  the  proper  number  of  meshes  but  the  wire  from 
which  the  cloth  is  woven  may  be  larger  or  smaller  than  the 
size  called  for  in  the  standard  method.  This  will  reduce  or  in- 
crease, as  the  case  may  be,  the  size  of  the  openings  of  the  sieve. 
Not  only  may  the  sieves  vary  from  the  standard  by  reason  of 
incorrect  mesh,  but  also  by  reason  of  irregular  spacing.  That 
is,  the  wires  may  be  nearer  together  in  some  places  than  in 
others,  leaving  large  openings  at  the  latter  points  for  the  cement 
to  drop  through. 

On  purchasing  sieves  they  should  be  examined  as  to  the  regu- 
larity of  the  spacing  by  holding  them  to  the  light  and  also  the 
number  of  meshes  to  the  inch  should  be  counted.  For  this  latter 
purpose,  small  magnifying  glasses  such  as  are  used  for  testing 
linen  are  convenient.  These  consist  of  a  small  lens,  mounted  on 
a  stand,  in  the  base  of  which  is  an  opening  exactly  one-half  inch 
square.  The  opening  is  placed  over  various  parts  of  the  sieve  and 
the  number  of  meshes  counted.  Where  such  an  instrument  is 
not  at  hand,  an  opening  of  this  size  may  be  cut  in  a  piece  of  card- 
board and  the  meshes  counted  by  the  aid  of  a  small  reading  or 
pocket  magnifying  glass.  Sieves  may  also  be  calibrated  by  com- 
paring them  with  other  sieves  of  known  value.  Or  a  sample  of 
standard  ground  quartz  may  be  kept  for  this  purpose.  Any 


388  PORTLAND  CEMENT 

holes  or  irregularities  in  test  sieves  should  be  stopped  up  with 
solder. 

A  convenient  balance  for  use  in  making  sieve  tests  is  shown  in 
Fig.  119.     The  beam  is  graduated  into  i/iooo  of  a  pound,  hence 


Fig.  119. — Balance  tor  fineness  test. 

if  one-tenth  pound  (=•  about  45  grams)  is  taken  for  the  test  each 
of  the  small  divisions  on  the  beam  will  represent  o.i  per  cent 
residue. 

OTHER  METHODS. 
Methods  of  Sieving,  Sieves,  Etc. 

Where  many  sievings  have  to  be  made  every  day,  the  use  of  a 
sieve  without  top  and  bottom  is  the  general  plan.  In  this  case 
the  sieving  is  done  over  a  large  piece  of  paper  or  oilcloth.  When 
it  is  desired  to  ascertain  if  the  operation  has  been  completed,  the 
material  on  the  paper  is  rolled  to  one  side  by  lifting  the  edge  of 
the  paper,  thus  exposing  a  clean  surface  over  which  the  sifting 
may  be  continued  and  the  amount  passing  through  the  sieve  ob- 
served. An  experienced  operator  will  be  able  to  tell,  by  his  eye 
and  sense  of  time,  when  the  operation  is  finished,  without  re- 
course to  balance  and  weights.  In  place  of  striking  the  sieve 
against  the  palm  of  the  hand  some  operators  bounce  one  side  of 
it,  gently  up  and  down,  on  a  small  block  of  wood,  taking  care  not 


Fig.  120.— Sieving  apparatus.,  F.  I,.  Smidth  &  Co. 


FINENESS  389 

• 

to  bounce  any  of  the  material  over  the  top  of  the  sieve.  The  use 
of  shot  also  greatly  hastens  the  operation  of  sieving,  as  the  bounc- 
ing of  these  latter,  on  the  wire  cloth  of  the  screen,  keeps  the 
meshes  of  the  latter  open.  To  separate  the  shot  from  the  coarse 
material  preparatory  to  weighing  the  latter,  pass  the  mixture 
through  a  10  or  20  mesh  screen. 

When  tests  are  made  by  using  sieves  without  a  top  the  sides 
of  these  should  be  high  in  order  to  avoid  bouncing  the  material 
out  of  the  'apparatus.  If  the  sieving  is  done  by  bouncing  the 
sieve  up  and  down  on  a  block  the  sides  of  the  sieve  should  be  at 
least  six  inches  high. 

At  the  mill  where  cement  is  usually  tested  fresh  as  it  comes 
from  the  grinders,  it  is  unnecessary  to  dry  it  at  100°  C.  before 
making  the  test,  but  when  inspecting  cement  which  has  been 
stored,  it  should  always  be  thoroughly  dried  before  making  the 
sieve  test.  Descriptions  of  various  forms  of  drying  ovens  are 
given  on  page  298. 

'  Various  forms  of  mechanical  shakers  for  doing  away  with  the 
manual  labor  incident  to  hand  sieving  have  been  devised  and 
are  occasionally  used  in  spite  of  the  fact  that  the  hand  method 
is  specified  by  the  standard  methods  of  testing.  None  of  them 
has  found  general  use,  however,  and  indeed  for  the  most  part 
they  seem  to  be  confined  to  college  laboratories  or  small  testing 
laboratories. 

One  of  the  best  forms  of  mechanical  shaking  sieves  is  that 
shown  in  Fig.  120.  This  apparatus  is  of  European  origin  and 
is  imported  into  this  country  by  F.  L.  Smidth  &  Co.,  of  New 
York  City,  the  well  known  manufacturers  of  cement  machinery. 
It  consists  of  a  shaking  device  which  gives  an  up  and  down 
motion  only,  but  many  strokes  a  minute,  which  is  driven  by  a 
small  motor. 

Prof.  J.  M.  Porter  described  in  a  paper  read  before  the  Ameri- 
can Society  for  Testing  Materials  his  sieve  shaker  a  working 
drawing  of  which  is  given  in  Fig.  121.  This  arrangement  rocks 
the  sieve  in  both  the  vertical  and  horizontal  planes.  Prof.  T. 


390 


PORTLAND  CEMENT 


R,  Lawson  describes  a  somewhat  simpler  device  in  Engineering 
Neivs,  Dec.  30,  1909,  p.  728,  to  which  the  reader  is  referred  for 


IH 

• 

:ji^.-.::; 

Fig.  i2i.— Details  of  I^afayette  College  cement  sieve  for  testing 
cement  as  originally  designed. 

a  description.     The  author  tried  this  arrangement,  however,  and 
found  it  to  be  far  from  satisfactory. 

DETERMINING  THE  FLOUR  IN  CEMENT. 

A  number  of  devices  have  been  proposed  for  determining  the 
flour  in  cement.  The  chief  difficulty  with  them  all  seems  to  be 
standardization.  Each  one  will  give  a  different  result  from  the 
other,  as  we  would  suppose,  for  there  is  no  specification  as  to 
what  is  meant  by  flour,  and  each  apparatus  takes  out  a  size  differ- 
ent from  the  other. 

Practically  all  of  these  forms  of  apparatus  depend  upon  the 


FINENESS  391 

suspension  of  the  finer  particles  of  the  cement  in  air,  benzine, 
kerosene,  water,  etc.  A  number  of  them  were  described  in  The 
Engineering  Record  of  August  20,  1904,  page  234.  As  we  have 
said,  the  difficulty  with  all  of  them  is  that  each  would  report  a 
different  percentage  of  the  cement  as  flour.  Even  if  they  were 
so  calibrated  as  to  give  concordant  results,  these  figures  would 
mean  nothing  more  than  the  sieve  test  carried  a  little  further. 
We  do  not  know  how  fine  cement  has  to  be  ground  in  order  to 
"carry  sand,"  although  we  know  that  it  must  be  ground  con- 
siderably finer  than  merely  sufficient  for  it  to  just  pass  the  200- 
mesh  sieve.  For  experimental  purposes  it  is  highly  important 
to  obtain  some  form  of  apparatus  which  will  enable  the  finer 
particles  of  the  cement  to  be  sorted  out  and  graded,  in  order  that 
the  point  of  fineness  at  which  the  sand  carrying  capacity  begins 
to  approach  that  of  ordinary  commercial  cements  may  be  deter- 
mined. Such  an  apparatus,  after  this  point  has  been  determined, 
would  have  a  practical  value,  because  of  two  cements  the  one 
having  the  greatest  percentage  of  such  "active"  particles  would 
be  the  best  ground. 

The  Germans  now  employ  a  sieve  having  250  meshes  to  the 
inch  as  a  standard  in  place  of  the  No.  200  American  standard. 
Messrs.  J.  Gantois  et  Cie  of  St.  Die,  France  (Ebstein  Bros.,  60 
Grand  St.,  New  York)  advertise  a  300  mesh  sieve.  Both  of 
these  sieves  will  be  found  of  use  in  studying  the  fineness  of 
cement.  Neither  of  them  however  is  fine  enough  to  pass  only 
active  material  and  reject  all  coarse  or  inactive  particles  and  for 
this  latter  recourse  must  be  had  to  one  of  the  suspension  methods 
given  below.  Something  may  be  gained  by  determining  the  fine- 
ness on  the  No.  100,  No.  200  and  No.  250  sieves  and  plotting 
the  results  into  a  curve  of  which  one  set  of  ordinates  represents 
the  percentage  of  material  passing  and  the  other  the  area  of  the 
openings  of  the  screen. 

Suspension   Method. 

The  form  of  apparatus  devised  by  the  author  for  determining 
the  flour  in  cement  by  suspension  in  a  liquid  is  modeled  after 
the  silt  cylinders  used  for  soil  analysis.  Fig.  122  shows  the 


392 


PORTLAND  CEMENT 


apparatus.  It  consists  of  a  cylinder  of  at  least  300  mm.  height 
and  not  too  great  diameter  provided  with  a  cork  or  stopper  for 
closing  it  and  a  siphon  for  drawing  off  the  liquid  and  suspended 
matter.  The  lower  end  of  the  siphon  is  closed  by  a  rubber  tube 
and  pinch-cock  and  the  upper  one  is  bent  as  shown.  Strips  of 
paper  or  file  marks  are  made  on  the  cylinder,  one  near  the  top 
and  the  other  exactly  200  mm.  below  this  one.  In  use,  100  grams 
of  cement  are  introduced  into  the  cylinder  and  the  latter  filled 


Fig.  122.— Apparatus  for  determining  flour. 

with  kerosene  freed  from  water  (as  described  on  page  363  under 
specific  gravity)  to  the  upper  mark  and  shaken  well.  It  is  then 
placed  on  a  block,  the  siphon,  which  should  be  full  of  kerosene 
inserted  until  its  opening  is  level  with  the  lower  mark,  and 
exactly  10  seconds  after  the  cylinder  was  placed  on  the  block  the 
pinch-cock  is  to  be  opened  and  the  liquid  siphoned  off  to  the 


FINENESS 


393 


lower  mark.  This  process  is  repeated  until  the  liquid  above 
the  lower  mark  settles  practically  clear  in  10  seconds.  The  resi- 
due in  the  cylinder,  or  else  the  suspended  matter,  is  then  collected 
on  a  filter  and  its  weight  determined.  From  this  the  percentage 
of  flour  is  calculated  and  reported  as  "particles  having  a  settl- 
ing value  in  kerosene  of  less  than  20  millimeters  per  second." 
These  can  be  again  divided  into  two  portions,  by  allowing  15 
seconds  to  settle,  when  the  value  will  be  200-^-15  or  13^  mm. 
per  second,  etc. 

If  desired,  the  size  of  the  largest  of  these  particles  can  then  be 
measured  under  the  microscope. 

The  Griffin-Goreham  Flourometer. 
The  Griffin-Goreham  standard  flourometer  is  shown  in  Fig. 


Fig.  123. — Griffin-Goreham  flourometer. 

123  and  is  used  to  some  extent  in  England.     The  Braun  Ap- 
paratus Co.,  Los  Angeles,  Cal.,  are  the  American  importers.  This 


394 


PORTLAND  CEMENT 


apparatus  consists  of  two  parts.  An  aerometer  or  blower  and 
the  apparatus  proper  or  flourometer.  The  blower  consists  of  the 
customary  bell  and  water  tank  and  is  merely  used  to  furnish  a 
constant  supply  of  air  to  the  apparatus.  The  flourometer  itself 
(Fig.  124)  consists  of  a  long  brass  tube,  T  resting  upon  a  stand. 
The  separation  of  the  coarse  and  fine  particles  takes  place  in 
this.  The  tube  is  surmounted  by  a  double  walled  dome,  W, 
covered  with  a  top,  0.  The  walls  of  this  dome  are  perforated 


Fig.  124.— Griffin-Goreham  flourometer,  detail. 

and  the  spaces  in  between  them  (W}  are  filled  with  cotton. 
This  serves  to  catch  all  the  dust  and  prevents  this  being  blown 
into  the  laboratory.  The  lower  part  of  the  brass  tube,  T, 
terminates  in  a  cone-shaped  brass  casting,  F,  which  rests  upon 
the  stand.  A  three-way  stop-cock  provided  with  a  pointer  to 
show  the  direction  of  the  opening,  is  placed  at  the  lower  end  of 
the  cone  and  beneath  this  a  glass  tube  R,  which  serves  to  catch 
the  coarse  particles. 


FINENESS  395 

The  sample  of  cement  should  be  dried  for  an  hour  at  110°. 
The  pointer  of  the  stop-cock  should  be  at  right  angles  to  the 
brass  tube  T.  The  tube  T  is  removed  and  about  one  gram  of  the 
cement  is  then  introduced  into  the  funnel  F.  The  bell  of  the 
aerometer  is  now  raised  to  its  full  extent  and  the  air  pressure 
noted. 

The  pointer  of  the  stop-cock  is  next  turned  parallel  with  the 
tube  and  the  air  allowed  to  blow  through  the  apparatus  for  ten 
minutes.  At  the  end  of  this  time  the  air  pressure  is  turned  off, 
when  the  coarse  particles  from  which  the  cement  has  been 
separated  drop  into  the  receptacle  R.  This  residue  is  weighed 
and  the  difference  is  of  course  flour. 

Any  blower  which  will  furnish  air  at  a  steady  and  standard 
pressure  may  be  used  in  place  of  the  aerometer  described.  Two 
large  cans  set  at  constant  vertical  distances  apart,  such  as  one 
on  the  table  and  one  on  the  floor,  for  instance,  will  serve,  the 
upper  one  being  filled  with  water  which  flows  into  the  lower, 
forcing  out  the  air  in  the  latter.  The  objection  to  all  these 
water  blowers  is  of  course  the  fact  that  the  air  is  more  or  less 
damp.  Best  results  will  be  obtained  by  passing  the  air  through 
a  rather  large  drying  tower  filled  with  calcium  chloride  or  better 
still  pumice  stone  drenched  with  strong  sulphuric  acid. 

I  have  found  this  apparatus  in  general  more  satisfactory  than 
the  Gary-Lindner  apparatus  described  below.  On  the  other  hand 
the  Gary-Lindner  apparatus  is  of  course  suitable  for  collecting  a 
quantity  of  flour  of  various  degrees  of  fineness  and  testing  this 
with  sand  for  strength.  At  the  present  time  no  very  satisfactory 
apparatus  is  at  hand  and  no  one  of  the  three  methods  given 
can  be  said  to  give  even  fair  results.  Some  idea,  however,  can 
be  formed  as  to  the  amount  of  flour  by  studying  various  ce- 
ments under  exactly  the  same  conditions,  and  the  writer  has  em- 
ployed them  to  advantage  in  studying  the  various  types  of  grind- 
ing machinery  with  reference  to  the  relative  amount  of  flour  pro- 
duced by  these  latter. 

The  Gary-Lindner  Apparatus. 
The  apparatus  (Fig.  125)  consists  of  three  glass  tubes,  a,  the 


396 


PORTLAND  CEMENT 


lower  ends  of  which  are  united  by  pieces  of  large  rubber  tubing 
to  three  glass  funnels  into  which  small  glass  tubes  have  been 
melted.  Through  these  small  tubes  air  is  supplied,  The  cement 
must  be  first  dried  perfectly.  Twenty  grams  of  the  cement  to  be 
tested  are  placed  in  the  funnel  I,  then  air  is  blown  in  at  a  pressure 
of  100  mm.,  water  column.  The  glass  cocks  permit  the  adjust- 
ment of  the  air  supply  to  each  funnel ;  the  pressure  is  noted  on  the 


Fig.  125.— Gary-Lindner  apparatus. 

U-manometer.  The  funnels  I,  II,  III  will  enter  into  operation 
one  after  the  other  and  at  the  end  there  will  remain  a  quantity  of 
powder  in  each  of  the  funnels.  The  finest  flour  will  pass  out 
of  the  glass  tube  III  and  will  be  arrested  in  the  glass  receptacle, 
IV.  If  the  air  pressure  is  produced  by  a  hydraulic  blower,  the 
air  must  be  dried  before  entering  the  funnels,  as  described  above. 

OBSERVATIONS  ON  FINENESS. 
Effect  of  Fineness  on  the  Properties  of  Portland  Cement. 
The  effect  of  the  fineness  to  which  Portland  cement  clinker  is 


FINENESS  397 

ground  upon  the  physical  properties  of  the  resulting  cement 
is  well  understood  as  the  following  quotation  from  the  Progress 
Report  of  the  American  Society  of  Civil  Engineers  will  show; 

"18.  Significance.  It  is  generally  accepted  that  the  coarser 
particles  in  cement  are  practically  inert,  and  it  is  only  the  ex- 
tremely fine  powder  that  possesses  adhesive  or  cementing  quali- 
ties. The  more  finely  cement  is  pulverized,  all  other  conditions 
being  the  same,  the  more  sand  it  will  carry  and  produce  a  mortar 
of  a  given  strength." 

The  two  properties  of  cement  most  affected  by  the  fineness 
of  the  product  are  the  setting  time  and  the  sand  carrying  capac- 
ity. All  the  properties  of  the  cement  are  of  course  influenced 
to  some  degree. 

Influence   on   Color. 

The  color  of  clinker  itself  is  practically  black.  As  the  clinker 
is  ground  the  color  becomes  lighter,  until  at  a  fineness  of  75  per 
cent,  passing  the  No.  200  test  sieve,  the  color  of  the  commercial 
product,  a  light  buff,  is  reached.  Cement  ground  so  fine  that 
95  or  loo  per  cent,  of  it  will  pass  the  No.  200  test  sieve  is  of 
a  somewhat  lighter  shade  than  cement  ground  to  the  ordinary 
fineness  of  75  per  cent,  passing  this  sieve.  At  the  same  time, 
no  manufacturer  would  care  to  go  to  the  increased  expense 
of  grinding  the  cement  to  such  an  extreme  degree  of  fineness 
merely  for  the  sake  of  a  slightly  lighter  color,  nor  would  even 
sidewalk  and  concrete  block  men  care  to  pay  the  increased  cost 
of  such  cement  simply  to  obtain  cement  of  a  slightly  lighter 
shade. 

Influence  on  Soundness. 

Fine  grinding  will  to  some  extent  help  the  soundness  of  the 
cement.  This  is  shown  by  Table  XXVIII. 

This  gives  four  instances  in  which  soundness  was  helped  by 
fine  grinding,  but  in  order  to  obtain  four  instances  many  samples 
of  unsound  cement  were  ground,  and  the  majority  of  them  failed 
to  become  sound  even  after  being  ground  to  an  impalpable  pow- 
der. Fine  grinding  and  seasoning,  however,  usually  produced 
the  desired  results.  That  is,  an  unground  cement  after  season- 


398 


PORTLAND  CEMENT 


ing,  say  one  week,  failed  to  pass  the  boiling  test,  but  the  same 
cement  ground  so  fine  that  none  of  it  remained  on  the  No.  200 
test  sieve  passed  the  test  after  seasoning  one  week.  The  grind- 
ing no  doubt  here  breaks  up  the  small  pieces  of  clinker  and 
allows  the  air  to  slake  out  the  injurious  component.  In  this 
connection,  it  may  be  said,  that  if  the  coarse  particles,  i.e.,  those 
remaining  on  the  No.  200  sieve,  are  separated  from  the  cement 
and  ground  to  a  fineness  of  75  per  cent,  through  the  No.  200 
sieve,  the  resulting  product  is  usually  unsound.  It  is  also  usual- 
ly quick-setting,  due  to  the  fact  that  the  sulphate  nearly  all 
passes  into  the  fine  powder.  If  i  per  cent,  of  plaster  of  Paris  is 
added  to  the  powder,  its  setting  time  is  normal  but  it  is  still 
unsound.  If  the  powder  is  then  seasoned  for  a  few  days  it  be- 
comes sound. 

TABLE  XXVIII. — SHOWING  EFFECT  OF  FINK  GRINDING  OF  CEMENT 
ON  SOUNDNESS. 


Result  of  five-hour  steam  test  (A.  S 

C.  K.). 

As  received 

Ground  to  pass  No.  200  sieve 

Ground  to  an 
impalpable  powder 

Checked 

Checked 

Checked 

Slightly  checked 

Sound 



Checked 

Slightly  checked 

Sound 

It  would,  however,  be  a  waste  of  energy  for  the  manufacturer 
to  make  a  sound  cement  by  grinding  one  unsound  at  ordinary 
fineness  to  say  100  per  cent,  passing  a  No.  200  test  sieve,  as  by 
grinding  the  much  softer  raw  materials  to  a  fineness  of  only  95 
to  98  per  cent,  through  the  loo-mesh  sieve  he  would  be  practical- 
ly sure  of  obtaining  the  same  results,  provided  the  composition  of 
the  mixture  and  the  burning  of  the  clinker  were  satisfactory. 
At  the  same  time,  if  the  manufacturer  found  it  advantageous  to 
grind  his  cement  to  a  fineness  of  90  to  95  per  cent,  through  a 
No.  200  test  sieve,  he  would  find  that  it  had  some  beneficial 
effect  upon  the  soundness  also,  and  that  this  effect  was  most 
marked  where  the  cement  had  a  chance  to  season  or  age  as  it 
usually  does. 


FINENESS 


399 


Influence  on  Setting  Time. 

The  influence  of  fineness  upon  the  rate  of  set  of  cement  is  in 
some  instances  quite  marked ;  in  other  instances  this  is  much  less 
noticeable.  If  any  effect  is  produced  at  all,  and  there  generally 
i$,  it  is  to  make  the  cement  quicker  setting, — in  some  instances, 
'so  quick-setting  as  to  be  unfit  for  use':  and  often,  where  this  is 
the  case,  additions  of  plaster  of  Paris  fail  to  retard  the  set  suffi- 
ciently to  allow  the  cement  to  be  used.  In  Table  XXIX  are  given 
a  number  of  instances  illustrating  the  influence  of  fine  grinding 
upon  setting  time. 

TABLE  XXIX. — INFLUENCE  OF  FINE  GRINDING  OF  CEMENT  UPON 
ITS  SETTING  TIME. 


Cement  number 

Per  cent,  passing  a  No.  200  sieve. 

75 

80 

85 

90 

95 

IOO 

Setting  time  (initial  set)  in  minutes. 

255 
105 
120 
240 
240 
2OO 
IOO 
H5 

246 

106 
H5 

200 
210 
190 
IOO 

105 

192 

IOO 
IOO 

180 
no 

175 
90 

IOO 

75 

IOO 

95 
H5 

55 

IOO 

80 
75 

12 
22 
60 
60 
15 
25 
25 
30 

2 

6 
35 
30 
5 

2 

5 
10 





6  

•  •••  
8                                    ... 

The  question  of  the  influence  of  fine  grinding  upon  the  set 
is  an  important  one,  for  upon  this  will  depend  to  a  large  degree 
the  ability  to  grind  cement  to  the  point  where  all  of  it  is 
rendered  useful,  and  where  it  contains  no  inert  matter  except 
that  present  chemically  and  not  due  to  coarseness.  (The  compo- 
•  sition  of  the  cement  unquestionably  has  something  to  do  with 
the  effect  of  fine  grinding.  High-alumina  and  low-lime  cements 
seem  to  have  their  setting  time  most  affected  by  finer  grinding. 
High  lime,  soft-burned  and  low-alumina  cements  do  not  seem  to 
be  so  much  affected. 

Cements  low  in  lime  are  often  quick-setting,  and  if  a  sample 
of  cement  is  sieved  through  a  No.  200  test  sieve  and  analyses  are 


4OO  PORTLAND    CEMENT 

made  of  both  the  coarse  residue  and  the  fine  portion  passing,  the 
former  will  in  most  cases  be  found  lower  in  lime  than  the  latter. 
It  is  natural  that  the  softer  portions  of  the  clinker  should  consti- 
tute the  greater  part  of  the  impalpable  powder  in  ordinary 
Portland  cement.  When  the  cement  is  ground  still  finer  the 
harder  portions  also  are  broken  up,  and  these  harder  portions  are 
probably  responsible  for  the  "quick  set"  of  finely  ground  cement, 
owing  to  the  fact  that  they  are  lower  in  lime  and  are  burned  to  a 
high  degree  of  vitrifaction.  It  is  certainly  possible,  even  prob- 
able, that  if  it  is  found  advantageous  to  grind  cement  to  a  much 
greater  degree  of  fineness  than  is  now  practiced,  it  will  also  be 
found  necessary  to  grind  the  raw  material  to  a  higher  degree 
of  fineness,  in  order  to  allow  the  making  of  very  highly  basic  ce- 
ment, in  which  the  highest  possible  amount  of  lime  is  obtained. 
If  it  is  desirable  to  get  rid  of  all  the  physically  inert  material 
by  fine  grinding  of  the  clinker,  it  is  also  equally  desirable  to  have 
in  the  cement  all  of  the  chemically  active  element  possible. 

I  am  strongly  inclined  to  believe  that  it  will  be  possible  to 
grind  cement  very  fine  without  influencing  the  set  unfavorably, 
by  properly  adjusting  the  composition  of  the  clinker  and  the 
degree  of  burning.  If  the  finer  particles  of  cement,  not  merely 
the  particles  which  pass  a  No.  200  sieve  but  the  impalpable  dust, 
are  separated  from  the  cement,  it  will  usually  be  found  that  this 
very  fine  material  sets  normally,  showing  that  it  is  possible  to 
grind  some  part  .of  the  cement  at  least  to  an  impalpable  powder. 
It  is  also  now  generally  agreed  that  it  is  this  fine  powder  which 
is  the  active  constituent  in  cement.  Hence  it  follows  that  the 
active  portion  of  cement  is  not  quick-setting  even  when  finely 
ground,  and  that  there  is  some  undesirable  element  in  the  coarser 
and  at  present  inert  particles  of  the  cement  which  is  liberated 
or  rendered  active  by  the  grinding.  The  problem  will  there- 
fore undoubtedly  be  to  keep  out  the  undesirable  element  from  the 
clinker  and  to  increase  the  desirable  one.  I  have  no  doubt  that 
by  the  time  grinding  machinery  has  been  perfected  which  will 
reduce  cement  to  the  fineness  of  100  per  cent,  through  a  No.  200 
test  sieve  on  a  commercial  basis,  the  chemical  side  of  the  ques- 


FINENESS 


401 


tion  will  have  been  solved.  Indeed,  experiments  which  I  have 
made  indicate  a  solution  of  the  problem.  Under  present  con- 
ditions it  would  be  practically  impossible  to  produce  commercial- 
ly a  cement  much  finer  than  90  per  cent,  passing  a  No.  200  sieve, 
if  indeed  it  would  be  possible  to  reach  even  this  fineness,  and 
at  this  nothing  more  than  a  slight  shortening  of  the  setting  time 
of  properly  proportioned  cements  should  be  met  with. 

Effect  of  Fineness   upon  Strength. 

A  number  of  experiments  made  by  the  author  to  determine  the 
effect  of  finer  grinding  upon  the  tensile  strength  of  Portland 
cement  proved  the  following  general  facts. 

1.  That  the  neat  strength  is  lowered  by  finer  grinding. 

2.  That  the  sand  strength  is  increased  by  finer  grinding. 
Table  XXX  gives  the  results  obtained  in  one  of  the  most  care- 
fully made  of  these  tests. 

Referring  to  Table  XXX  we  see  that  the  neat  strength  is  de- 
creased by  fine  grinding.  This  decrease  is  as  follows:  Grind- 
ing to  85  per  cent,  fine  decreases  the  7  day  neat  tensile  strength  17 

TABLE  XXX.— STRENGTH  OF  THE  SAME  CEMENT  GROUND  TO  VARIOUS 
DEGREES  OF  FINENESS. 


Age  in  days 

Per  cent,  passing  a  No.  100  sieve. 

Neat  or  sand 

93-9 

95-8 

97-4 

990 

IOO.O 

Per  cent,  passing  a  No.  200  sieve. 

80 

85 

90 

95 

100 

Tensile  strength  in  Ibs.  per  sq.  in. 

Neat 
Neat 
Neat 

i  :  3  sand 
i  :3  sand 

i  :  4  sand 
i  :  4  sand 

369 

955 
963 

235 
297 

160 
224 

241 
796 
849 

284 

353 

204 
266 

308 
740 
775 

35i 

468 

234 
324 

282 

627 
626 

® 

247 

377 

200 
558 

594 

382 
576 

263 
392 


28      

?Q                                                          ... 

2I::::::::  

NOTE. — Each  value  is  based  on  five  briquettes.     Each  portion   is  from 
cement.     One  operator  made  all  tests. 
26 


lot  of 


402 


PORTLAND    CEMENT 


per  cent,  from  the  figures  of  the  80  per  cent.  fine.  Grinding  to  o/> 
per  cent,  fine  decreases  the  strength  21  and  20  per  cent,  respec- 
tively for  the  same  periods.  Grinding  to  95  per  cent,  fine  de- 
creases the  strength  34  and  35  per  cent,  and  grinding  to  100  per 
cent,  fine  decreases  it  42  and  38  per  cent.  In  general  it  will  be 
seen  that  the  decrease  in  neat  strength  due  to  fine  grinding  is 
about  the  same  for  both  the  7  day  and  the  28  day  periods. 

Referring  to  the  sand  tests  it  will  be  seen  at  a  glance  that  the 
increase  in  sand  strength  due  to  finer  grinding  is  large.  In- 
creasing the  fineness  from  80  to  85  per  cent.,  increases  the  7  day 
1 13  sand  strength  21  per  cent. ;  further  grinding  to  90  per  cent, 
increases  it  to  45  per  cent. ;  grinding  to  95  per  cent,  increases 
it  to  54  per  cent.,  while  grinding  to  100  per  cent,  increases  it  to 
63  per  cent,  over  the  80  per  cent,  strength.  The  1 14  sand 
strength  is  increased  by  practically  the  same  percentage.  The 
increase  upon  the  28  day  sand  tests  due  to  finer  grinding  is  even 
larger. 

In  this  series  of  tests  the  original  cement  gained  but  little  neat 
strength  between  these  two  periods.  Fine  grinding  will  decrease 
not  only  the  neat  strength  but  also  the  percentage  of  gain  between 
these  two  periods  as  well.  An  example  of  this  is  given  below. 
In  this  experiment  a  lot  of  cement,  just  as  received  from  the 
TENSILE  STRENGTH  IN  POUNDS  PER  SQUARE  INCH. 


Neat 

i  day 

7  days 

28  days 

3  mos. 

6  mos. 

i  year 

2  years 

•727 

6  "?o 

72? 

7  2O 

760 

82^ 

Sco 

Ground  to  pass  a 
No.  200  sieve  •  •  • 

6^/ 
210 

525 

f*D 

540 

540 

560 

575 

560 

I 

:  3  morta 

r 

i  day 

7  days 

28  days 

3  mos. 

6  mos. 

i  year 

2  years 

As  received  
Ground  to  pass  a 
No.  200  sieve  .  •  . 

... 

278 
480 

357 
555 

387 

575 

390 
615 

410 
623 

425 
640 

mills,  was  divided  into  two  parts,  one  of  which  was  tested  just 


403 

as  it  was  and  the  other  was  ground  to  completely  pass  a  No. 
200  sieve,  and  then  tested.  On  page  402  are  the  results  ob- 
tained on  the  two  samples. 

Limitations  of  the  Sieve  Test. 

The  fineness  to  which  cement  is  ground  is  an  important  point. 
Since  cement  is  usually  used  with  sand,  the  strength  of  the  mor- 
tar increases  with  the  fineness  of  the  cement,  because  the  greater 
is  the  covering  power  of  the  cement,  i.  e.,  the  more  parts  of 
cement  come  into  action  with  the  sand.  A  test  for  fineness  is 
nearly  always  included  in  cement  specifications,  as  the  indications 
from  a  fair  degree  of  fineness  coupled  with  proper  tensile 
strength,  neat,  are  that  the  cement  will  give  good  results  when 
used  with  sand. 

At  the  same  time  the  most  rigid  fineness  specification  could  be 
filled  by  a  cement  which  would  be  many  degrees  too  coarse.  Some 
of  the  older  specifications  could  be  easily  filled  by  a  product  which 
would  show  almost  no  setting  qualities  and  no  sand-carrying  ca- 
pacity. If  a  sample  of  clinker  is  crushed  in  an  iron  mortar  by  a 
pestle  and  sieved  as  fast  as  it  is  ground  through  a  loo-mesh 
screen,  a  product  will  be  obtained  100  per  cent,  of  which  will  pass 
a  loo-mesh  screen.  Many  of  the  older  specifications  call  for  only 
90  per  cent.  If  a  pat  is  made  of  this  cement  it  will  just  about 
cohere.  If,  however,  the  fine  particles  are  sieved  through  a  200- 
mesh  screen  and  the  flour  washed  off  the  coarse  particles  by  ben- 
zine and  the  latter  driven  off  by  heat,  the  product  will  still  all 
pass  a  loo-mesh  sieve,  and  yet  will  have  no  setting  properties.  If 
another  sample  is  ground  in  a  mortar  and  sieved  after  every  few 
strokes  of  the  pestle  through  a  2oo-mesh  screen,  it  will  all  pass  a 
2OO-mesh  sieve  and  yet  will  nevertheless  be  almost  worthless  as 
a  cement.  When  washed  free  from  its  flour  with  benzine  it  will 
just  about  hold  together.  In  the  writer's  laboratory  there  was  a 
Braun's  gyratory  muller  for  grinding  samples,  in  whicfi  the  grind- 
ing is  done  by  an  enclosed  round  pestle  revolving  in  a  semi-hemi- 
spherical mortar.  In  the  bottom  of  the  mortar  is  a  hole  which  can 
be  stopped  by  a  plug.  The  grinding  may  be  done  in  two  ways, 


404 


PORTLAND    CEMENT 


one  by  feeding  the  sample  into  the  hopper  in  the  cover  and  allow- 
ing it  to  work  its  way  out  at  the  bottom,  then  sieving  out  the 
fine  material  from  the  coarse,  and  returning  the  latter  through  the 
grinder,  and  so  on  until  all  has  passed  the  sieve.  The  other,  by 
placing  the  plug  in  the  bottom  of  the  mortar  and  allowing  the 
pestle  to  work  upon  the  material  until  the  latter  has  reached  the 
desired  fineness.  Two  samples  of  cement  were  prepared  from  the 
same  lot  of  clinker  by  these  methods.  One  sample,  the  one  made 
by  passing  the  clinker  through  the  muller  and  sieving  out  the 
2OO-mesh  particles  after  each  grind,  would,  of  course,  all  pass  a 
2OO-mesh  sieve.  The  other  sample,  the  one  made  by  grinding  the 
whole  sample  to  the  desired  fineness  without  screening,  tested  96 
per  cent,  through  a  loo-mesh  sieve  and  76.5  per  cent,  through  a 
2oo-mesh  sieve.  Sand  briquettes  were  made  of  these  two  lots  of 
cement  with  the  following  results. 


7  days 
pounds 

28  days 
pounds 

3  months 
pounds 

6  months 
pounds 

Samples  made  by  grinding  and 
screening  to  fineness  (all  2oo-mesh) 
Grinding     to     fineness     without 
screening1  

Broke  in 
clips 

or  c 

Broke  in 
clips 

2QC 

Broke  in 
clips 

11A 

28 
•ziS 

**o 

-*yo 

324 

318 

The  cementing  value  of  Portland  cement  depends  upon  the  per- 
centage of  those  infinitesimal  particles  which  we  call  flour.  No 
sieve  is  fine  enough  to  tell  the  quantity  of  these  present.  At  the 
same  mill  it  is  probable  that  the  sieve  test  is  relative  but  to  the 
engineer  who  is  called  upon  to  examine  the  product  of  many  mills 
using  different  systems  of  grinding  the  sieve  test,  is  hardly  to  be 
expected  to  give  the  relative  percentage  of  flour  in  each.  The 
product  of  the  Griffin  mill  and  of  the  ball  and  tube  mill  probably 
differ  much  in  the  percentage  of  flour  present,  even  when  testing 
the  same  degree  of  fineness  on  the  2OO-mesh  sieve.  Even  with 
the  ball  and  tube  mill  system  one  ball  mill  and  two  tube  mills 
would  probably  give  a  product  with  a  higher  percentage  of  flour 
than  one  tube  mill  and  two  ball  mills,  even  when  the  cement  was 
ground  to  the  same  sieve  test.  The  size  screen  on  the  ball  mills 
probably  also  influences  the  percentage  of  flour  in  a  product  of  a 
certain  fineness. 


Chapter  XVI. 


TIME  OF  SETTING. 


STANDARD  SPECIFICATION  AND  METHOD  OF  TEST. 

Specification. — It  shall  develop  initial  set  in  not  less  than  thirty 
minutes,  but  must  develop  hard  set  in  not  less  than  one  hour,  nor 
more  than  ten  hours. 

Normal  Consistency. 

Method. — This  can  best  be  determined  by  means  of  Vicat  Nee- 
dle Apparatus,  which  consists  of  a  frame  (K),  Fig.  126,  bearing  a 
movable  rod  (Z,),  with  the  cap  {A)  at  one  end,  and  at  the  other 
the  cylinder  (B),  I  cm.  (0.39  in.)  in  diameter,  the  cap,  rod  and 
cylinder  weighing  300  gr.  (10.58  oz.)  The  rod,  which  can  be 
held  in  any  desired  position  by  a  screw  (F),  carries  an  indicator, 
\yhich  moves  over  a  scale  (graduated  to  centimeters)  attached 
to  the  frame  (K).  The  paste  is  held  by  a  conical,  hard  rubber 
ring  (/),  7  cm.  (2.76  ins.)  in  diameter  at  the  base,  4  cm.  (1.57 
ins.)  high,  resting  on  a  glass  plate  (/),  about  10  cm.  (3.94  ins.) 
square. 

In  making  the  determination,  the  same  quantity  of  cement  as 
will  be  subsequently  used  for  each  batch  in  making  the  briquettes 
(but  not  less  than  500  grams)  is  kneaded  into  a  paste,  as  describ- 
ed on  page  428  and  quickly  formed  into  a  ball  with  the  hands, 
completing  the  operation  by  tossing  it  six  times  from  one  hand  to 
the  other,  maintained  6  ins.  apart;  the  ball  is  then  pressed  into" 
the  rubber  ring,  through  the  larger  opening,  smoothed  off,  and 
placed  (on  its  large  end)  on  a  glass  plate  and  the  smaller  end 
smoothed  off  with  a  trowel ;  the  paste,  confined  in  the  ring,  resting 
on  the  plate,  is  placed  under  the  rod  bearing  the  cylinder,  which 
is  brought  in  contact  with  the  surface  and  quickly  released. 

The  paste  is  of  normal  consistency  when  the  cylinder  penetrates 
to  a  point  in  the  mass  10  mm.  (0.39  in.)  below  the  top  of  the  ring. 
Great  care  must  be  taken  to  fill  the  ring  exactly  to  the  top. 


406  PORTLAND 

The  trial  pastes  are  made  with  varying  percentages  of  water 
until  the  correct  consistency  in  obtained. 

Time  of  Setting. 

Method. — F'or  this  purpose  the  Vicat  Needle,  which  has  al- 
ready been  described,  should  be  used. 

In  making  the  test,  a  paste  of  normal  consistency  is  molded 
and  placed  under  the  rod  (Z,),  Fig.  126,  as  described;  this  rod, 


Fig.  126.— Vicat  needle.1 

bearing  the  cap  (D)  at  one  end  and  the  needle  (H),  I  mm. 
(0.039  in.)  in  diameter,  at  the  other,  weighing  300  gr.  (10.58 
oz.).  The  needle  is  then  carefully  brought  in  contact  with  the 
surface  of  the  paste  and  quickly  released. 

The  setting  is  said  to  have  commenced  when  the  needle  ceases 
to  pass  a  point  5  mm.  (0.20  in.)  above  the  upper  surface  of  the 
glass  plate,  and  is  said  to  have  terminated  the  moment  the  needle 
does  not  sink  visibly  into  the  mass. 


TIME:  OF  SETTING 


407 


The  test  pieces  should  be  stored  in  moist  air  during  the  test; 
this  is  accomplished  by  placing  them'  on  a  rack  over  water  con- 
tained in  a  pan  and  covered  with  a  damp  cloth  to^be  kept  away 
from  them  by  means  of  a  wire  screen ;  or  they  may  be  stored  in 
a  moist  box  or  closet. 

Care  should  be  taken  to  keep  the  needle  clean,  as  the  collection 
of  cement  on  the  sides  of  the  needle  retards  the  penetration,  while 
cement  on  the  point  reduces  the  area  and  tends  to  increase  the 
penetration. 

The  determination  of  the  time  of  setting  is  only  approximate, 
being  materially  affected  by  the  temperature  of  the  mixing  water, 
the  temperature  and  humidity  of  the  air  during  the  test,  the  per- 
centage of  water  used,  and  the  amount  of  molding  the  paste  re- 
ceives. 

NOTES. 

The  cheapest  form  of  moist  closet  consists  simply  of  a  wooden 
box  provided  with  a  door  and  shelves  and  painted  on  the  inside 


d. 


— -j- ;  ^  Z.'^Vl"!"!-.'1^  — ~~-T—  Zl 


Fig.  127.— Moist  closet. 

with  black  asphaltum  varnish  or  other  good  water-proof  paint 
(see  Fig.  127).  In  the  bottom  of  this  box  should  be  placed  a 
tin  pan  containing  a  sponge,  and  water  should  always  be  kept 
in  this  pan.  The  shelves  should  be  removable  and  may  be  made 
of  plate-glass  or  wood.  The  shelves  should  be  so  placed  as  to 


408  PORTLAND    CEMENT 

allow  a  free  circulation  of  air  through  all  parts  of  the  closet. 
Instead  of  being  painted  the  box  may  be  lined  with  thin  sheet 
zinc. 

A  common  tin  bread-box  makes  a  very  good  moist  closet 
where  only  a  few  pats  and  briquettes  have  to  be  tested.  This 
is  provided  with  a  few  cleats  and  a  perforated  tin  shelf  is  made 
to  fit  into  the  box,  and  rests  on  these  cleats.  Water  is  poured 
into  the  bottom  to  a  depth  of  a  half  inch  and  the  test  pieces  are 


Fig.  128.— Soapstone  moist  closet. 

placed  on  the  shelf.  In  order  to  prevent  rusting,  this  box  also 
should  be  painted  inside  with  black  asphalt  varnish. 

In  (large  laboratories  moist  closets  made  of  soapstone  have 
been  employed.  Such  a  closet,  used  in  the  Municipal  Laborato- 
ries of  the  city  of  Philadelphia,  is  shown  in  Fig.  128.  This 
closet  is  made  of  i%  mch  soapstone  (with  the  exception  of  the 
doors,  which  are  made  of  wood  covered  with  zinc)  and  is  in  two 
sections  for  the  reason  that  it  was  found  that  as  the  height  of  the 
closet  was  excessive,  the  humidity  varied  considerably  between 
top  and  bottom.  On  the  sides  of  each  closet  are  fastened  cleats 
to  hold  the  shelves,  which  are  of  glass  or  wood. 

Mr.  Ernest  B.  McCready  described  in  the  Proceedings  of  the 


TIME    OF    SETTING  409 

American  Society  for  Testing  Materials,  Vol.  VII,  a  moist  closet 
made  of  cement  which  is  employed  in  his  laboratory.  Such  a 
closet  can  be  constructed  in  any  cement  testing  laboratory  from 
waste  cement,  the  forms  being  made  by  a  local  carpenter.  A 
i  to  2  sand  mortar  was  used  and  the  walls  reinforced  with  one- 
half  inch  mesh  galvanized  wire  netting. 

Both  the  English  and  German  standard  specifications  call  for 
the  use  of  the  Vicat  needle.  The  German  specifications  pre- 
scribe that  "normal"  Portland  cement  shall  not  receive  its  initial 
set  in  less  than  one  hour,  and  fix  no  period  within  which  the 
final  set  shall  take  place.  The  English  standard  specifications 
divide  cement  into  three  grades,  "Quick,"  "Medium"  and  "Slow." 
The  requirements  for  the  three  are  as  follows: — "Quick,"  initial 
setting  time  not  less  than  two  minutes,  final  setting  time  not  less 
than  ten,  nor  more  than  thirty  minutes;  "Medium,"  initial  set- 
ting time  not  less  than  ten  minutes,  final  setting  time  not  less  than 
thirty  minutes  nor  more  than  two  hours ;  "Slow,"  initial  set  not 
less  than  twenty  minutes,  final  setting  time  not  less  than  two,  nor 
'more  than  seven  hours. 

OTHER  METHODS. 

The  test  proposed  by  General  Gilmore,  U.  S.  A.,  for  de- 
termining setting  properties  is  the  one  most  used,  in  this  coun- 
try. It  consists  in  mixing  cakes  of  neat  cement  from  2  to  3 
inches  in  diameter  and  y*  inch  thick  to  a  stiff  plastic  consistency 
and  observing  the  time  when  they  will  bear  a  needle  1/12  inch  in 
diameter  weighed  with  J4  pound.  This  is  noted  as  the  beginning 
of  the  set.  These  pats  should  be  made  with  a  flat  top  so  as  not 
to  catch  the  edge  of  the  needle.  Trials  are  next  made  every  now 
and  then  with  a  1/24  inch  in  diameter  needle  weighted  with  one 
pound.  The  time  at  which  the  cake  is  sufficiently  firm  to  bear 
this  latter  needle  is  noted  as  the  end  of  the  set.  Fig.  129  shows 
the  needles. 

The  Gilmore  needles,  or  wires,  are  much  more  convenient  to 
use  where  many  samples  have  to  be  tested,  as  the  pats  themselves 
do  not  have  to  be  lifted  from  the  moist  closet  or  table,  in  order  to 


4io 


PORTLAND    CEMENT 


apply  the  needle.  While  the  Vicat  needle  unquestionably  is  a 
much  more  scientific  instrument  and  should  be  used  where  great 
nicety  is  required  in  making  the  test,  as  in  settling  disputes,  etc. ; 


Fig.  129. — Gilmore  needles  for  testing  setting  time. 

still  for  ordinary  inspection  work,  where  all  that  is  needed  is  the 
assurance  that  the  cement  will  not  set  before  it  is  laid  in  position 
in  the  job,  and  that  after  it  is  so  placed  it  will  harden  in  a  rea- 
sonable time,  the  simpler  and  less  expensive  Gilmore  needles  will 
answer  the  purpose  just  as  well  as  the  more  expensive  Vicat  ap- 
paratus. The  Gilmore  needles  are  the  ones  generally  used  by 


6 


9  Fig.  130.— Gilmore  needles  mounted  on  stand. 

both  manufacturers  and  engineers  in  determining  the  setting  time 
of  cement,  and  most  of  those  called  upon  to  test  and  use  cement 
are  familiar  with  the  terms  initial,  and  final  set  as  defined  by  these 


TIME;  OF  SETTING 


411 


needles,  so  that  it  does  not  seem  to  have  been  a  very  wise  plan  on 
the  part  of  those  formulating  the  standard  rules  to  recommend 
that  the  test  be  made  with  the  Vicat  needle.  Setting  time  is 
influenced  by  so  many  things  besides  those  over  which  the  Vicat 
needle  has  control,  that  the  personal  equation  is  as  much  an  ele- 


Fig.  131.— Bramwell's  vicat  needle. 

ment  in  determinations  made  with  this  apparatus  as  with  those 
made  with  the  Gilmore  needles. 

Fig.  130  shows  an  arrangement  for  mounting  the  Gilmore  nee- 
dles so  that  they  always  bear  perpendicularly  and  evenly  upon  the 
top  of  the  pat. 

A  simpler  form  of  Vicat  needle  is  that  designed  by  J.  W. 
Bramwell.1  This  apparatus  is  shown  in  Fig.  131.  It  consists  of 
two  separate  rods,  each  weighing  300  grams.  One  of  these  rods 
is  fitted  with  a  cylinder,  one  cm.  in  diameter,  which  is  to  be  used 
for  determining  normal  consistency.  The  other  rod  is  provided 

1  Chemical  Engineer,  III,  i,  20. 


412  PORTLAND 

with  a  needle  of  I  mm.  diameter  for  the  setting  time  test.  The 
rods  are  graduated  so  that  the  penetration  can  be  read  by  means 
of  a  pointer  with  a  thumb  screw  to  hold  the  rods  at  any  height 
desired  and  the  rods  themselves  are  provided  with  stops  to  prevent 
them  from  falling  and  damaging  the  needle,  etc.  Whichever  rod 
is  not  in  use  is  held  upright  by  means  of  a  peg  fitting  in  a  hole 
in  the  top  of  the  rod,  as  shown  in  the  illustration.  A  glass  plate 
and  hard  rubber  ring  are  also  provided  with  this  apparatus,  as 
with  the  ordinary  Vicat  needle.  One  of  the  noteworthy  things 
about  the  Bramwell  apparatus  is  its  simplicity  and  low  price — • 
about  one-half  that  of  the  standard  Vicat. 

The  "ball"  test  for  determining  the  proper  consistency  is  much 
used  in  commercial  laboratories,  using  the  Gilmore  needles  to  de- 
termine set,  and  in  spite  of  its  crudeness,  gives  results  which 
agree  fairly  well  with  those  determined  by  the  Vicat  apparatus. 
It  consists  in  forming  the  mortar  into  a  ball  and  dropping  it  from 
a  height  of  one  foot.  This  fall  should  not  materially  flatten  nor 
crack  the  ball,  the  former  denoting  too  much  water  in  the  mortar 
and  the  latter  not  enough. 

In  most  plant  laboratories,  and  indeed  in  many  testing  lab- 
oratories where  Gilmore's  needles  are  used,  it  is  the  practice  to 
test  the  setting  time  of  cement  upon  a  smaller  batch  of  mortar 
than  that  prescribed  by  the  standard  rules.  Often  the  same  test 
piece  which  is  employed  for  setting  time  is  used  to  determine 
soundness  also  (see  Chapter  XVIII).  This  plan  consists  in  weigh- 
ing out  from  50  to  100  grams  of  cement.  This  is  placed  upon 
the  mixing  slab  and  a  small  crater  is  formed  in  the  center  of 
this.  The  water  is  next  added  in  a  measured  amount.  The 
cement  is  rolled  into  the  crater  and  the  mixture  is  worked  back 
and  forth  with  a  trowel  until  the  proper  plasticity  is  secured. 
The  working  usually  takes  from  one  to  three  minutes  depending 
upon  the  operator  and  the  quickness  of  his  movements.  The 
cement  is  then  formed  into  a  small  cake  which  is  placed  on  a 
small  glass  plate  (about  4  by  4  ins.)  and  flattened  out  with  the 
trowel  as  shown  in  Fig.  132,  so  as  to  present  a  smooth  surface 
to  the  needle.  If  the  pat  is  also  to  be  used  for  the  steam  test, 


TIME    OF    SETTING  413 

it  is  drawn  out  to  a  thin  edge  as  shown  in  Fig.  133.     For  this 
latter  test  the  pat  is  allowed  to  stand  in  the  moist  closet,  after 


Fig.  132.— Pat  for  determining  setting  time. 


Fig.  133.— Pat  for  determining  setting  time  and  soundness. 

the  setting  time  has  been  taken,  until  the  next  day,  when  it  is 
boiled  or  steamed. 

OBSERVATIONS  ON  SETTING  TIME. 

The  rapidity  with  which  cement  sets  furnishes  us  with  no  in- 
dication of  its  strength.  The  test  is  usually  made  to  determine 
the  fitness  of  the  material  for  a  given  piece  of  work.  For  ex- 
ample, in  most  submarine  work  a  quick-setting  cement  is  desired, 
that  is,  a  cement  which  loses  its  plasticity  in  less  than  half  an 
hour,  while  for  most  purposes  where  sufficient  time  will  be  given 
the  cement  to  harden  before  being  brought  into  use,  a  slow-set- 
ting cement  will  usually  answer  better,  or  one  that  sets  in  half  an 
hour  or  more.  The  slow-setting  cements  can  be  mixed  in  larger 
quantities  than  the  quick-setting,  and  do  not  have  to  be  handled 
so  quickly,  so  that  for  most  purposes  where  permissible  they  are 
used. 

When  cement  sets  hard  a  few  minutes  after  the  mortar  is  mix- 
ed it  is  said  to  have  a  "flash"  set.  Some  cements  are  so  quick 
setting  that  they  even  set  up  under  the  trowel  and  on  working 
get  dryer  instead  of  more  and  more  plastic. 

Factors  Influencing  the  Rate  of  Setting. 

(The  rate  of  set  is  determined  by  a  number  of  things,  ;  chief 
of  which  are  temperature  and  the  percentage  of  water  used  in 
making  the  mortar: — The  higher  the  temperature  the  quicker 
the  set  and  the  larger  the  percentage  of  water  the  slower  the 
set.\  Temperature  has  a  very  marked  influence,  and  many  ce- 


414 


PORTLAND    CEMENT 


ments  which  are  suitable  for  use  in  this  country  could  not  be  used 
in  the  Jropics.  Similarly  in  the  early  spring  and  late  fall  when 
the  temperature  out  of  doors  is  from  20°  to  30°  F.  below  that 
indoors,  cement  which  tests  up  quick  in  the  laboratory  may  give 
perfect  satisfaction  when  used  at  the  outside  temperature.  This 
influence  is  shown  by  the  results  given  below : 

TABLE  XXXI. — INFLUENCE  OF  TEMPERATURE  ON  THE  RATE  OF  SET- 
TING OF  PORTLAND  CEMENT. 


Temp. 

°F/ 

Sample  No. 

i 

2 

3 

4 

H. 

M. 

H. 

M. 

H. 

M. 

H. 

M. 

Initial  set 

3 

O 

5 

O 

2 

O 

2 

10 

35 

Final  set 

8 

O 

10+ 

•• 

6 

O 

6 

O 

Initial  set 

i 

5 

3 

O 

I 

15 

T 

5 

45 

Final  set 

3 

15 

7 

30 

3 

30 

3 

15 

60 

Initial  set 
Final  set 

o 

i 

30 

10     * 

2 

6 

30 

o 

o 

i 

15 
O 

o 
o 

3 

10 

80 

Initial  set 
Final  set 

o 
o 

4 

10 

2 

5 

00 

30 

o 
o 

2 

5 

.. 

Initial  set 

o 

45 

.'. 

.. 

.. 

.. 

IOO 

Final  set 

•• 

•• 

3 

IO 

•  • 

•  • 

•• 

•• 

The  percentage  of  water  used  to  gauge  the  pats,  or  in  actual 
work  to  make  the  mortar,  effects  the  setting  time,  as  well  as  the 
early  strength  of  the  concrete,  very  greatly.  A  wet  mixture  sets 
very  slowly,  while  a  dry  one  sets  much  more  promptly.  In  the 
manufacture  of  hollow  building  blocks,  where  the  piece  must  be 
removed  from  the  molds  at  once,  only  as  small  a  quantity  of 
water  as  is  actually  needed  to  do  the  work  is  used,  and  the  mix- 
ture of  about  the  consistency  of  damp  sand  is  rammed  into  the 
molds;  while  in  some  forms  of  concrete  construction,  the  mor- 
tar is  made  decidedly  plastic,  and  may  be  actually  poured  into 
the  forms.  It  is  then  left  several  days  to  harden  before  the  latter 
are  removed.  Below  are  given  some  results  on  the  effects  of 
various  percentages  of  water  on  the  setting  time  of  Portland  ce- 
ment: 

1  Of  room  during  setting  time  and  of  cement  and  of  water  used  to  gauge  pats. 


TIME    OF    SETTING 


415 


TABLE  XXXII.— INFLUENCE  OF  VARIOUS  PERCENTAGES   OF  WATER 

USED  TO  GAUGE  THE  PATS  ON  THE  SETTING  TIME  OF 

PORTLAND  CEMENT. 


Per- 
cent- 
age of 
water 

Sample  No. 

i  . 

2 

3 

4 

H. 

M. 

H. 

M. 

H. 

M. 

H. 

M. 

Initial  set 

0 

10 

2 

IO 

0 

10 

O 

2 

H 

Final  set 

2 

45 

6 

O 

O 

35 

0 

5 

,f. 

Initial  set 

o 

20 

2 

20 

O 

IO 

O 

25 

Final  set 

3 

50 

6 

O 

o 

35 

I 

o 

TQ 

Initial  set 

i 

5 

2 

2O 

0 

10 

.  . 

35 

Final  set 

5 

0 

6 

15 

0 

35 

I 

15 

Initial  set 

2 

10 

2 

40 

o 

8 

I 

25 

Final  set 

6 

20 

6 

15 

o 

30 

4 

o 

22 

Initial  set 
Final  set 

8 

2O 
O 

6 

0 
50 

o 

0 

5 
30 

2 

5 

15 
o 

Initial  set 

5 

10 

5 

0 

0 

20 

3 

0 

24 

Final  set 

12  + 

•• 

8 

30 

o 

50 

6 

10 

Another  factor  which  influences  very  greatly  the  rapidity  of 
the  set  of  cement  is  the  humidity  or  the  amount  of  water  vapor 
contained  in  the  air.  It  has  been  found  that  cement  will  al- 
ways set  much  more  slowly  in  a  moist  closet  than  it  will  when 
left  in  the  open  air  and  for  this  reason  test  pieces  upon  which 
the  setting  time  is  to  be  made,  should  always  be  kept  in  a  moist 
closet  and  should  not  be  allowed  to  remain  for  more  than  a 
minute  at  any  one  time  out  of  this. 

Rise  in  Temperature  During  Setting. 

It  was  formerly  the  practice  to  determine  the  rise  in  tempera- 
ture during  setting,  any  considerable  increase  being  considered 
as  indicative  of  free  lime  in  the  cement,  the  supposition  being 
that  the  rise  is  caused  by  the  heat  formed  by  the  hydration  of 
the  lime.  No  conclusion  could  be  more  erroneous.  From  the 
examination  of  many  samples  of  Portland  cement,  every  detail 
of  whose  manufacture  was  known,  I  am  not  afraid  to  say  posi- 
tively, that  the  rise  of  temperature  during  setting  is  not  only  not 


4l6  PORTLAND    CEMENT 

indicative  of  free  lime,  but  usually  comes  from  the  reverse,  not 
enough  lime.  Those  cements  which  show  the  greatest  increase 
in  temperature  during  the  process  of  setting  are  usually  the  quick- 
setting  cements.  These  cements  usually  are  low  in  lime  and 
burned  very  hard.  Many  samples  of  such  cements  show  a  rise 
of  temperature  distinctly  perceptible  to  the  hand,  and  yet  boiling 
for  many  hours  will  fail  to  disintegrate  the  pat  or  warp  or  check 
it  in  any  manner.  In  many  instances,  the  addition  of  a  small 
quantity  (l/2  per  cent.)  of  finely  ground  lime  or  i  or  2  per  cent, 
of  slaked  lime  will  slow  the  setting  of  the  cement,  and  in  this  case 
no  rise  of  temperature  will  be  met  with,  showing  that  the 
presence  of  free  lime  is  not  the  cause  of  the  rise  in  temperature 
during  setting.  On  the  other  hand  many  samples  which  fail 
badly  after  even  a  few  hours  of  the  steam  test,  show  no  greater 
rise  in  temperature  than  the  normal.  When  there  is  a  consider- 
able rise  in  temperature  during  the  setting  of  a  slow-setting  ce- 
ment, something  is  probably  wrong  with  the  cement,  but  when 
the  rise  is  met  with,  in  connection  with  quick  set,  it  is  no 
evidence  of  free  lime,  and  the  conclusion  that  it  is,  is  un- 
warranted by  facts. 

Influence  of  Sulphates  on  Setting  Properties. 

If  Portland  cement  clinker  is  ground  just  as  it  comes  from  the 
coolers,  without  the  addition  of  any  foreign  substance,  the  re- 
sulting cement  is  entirely  too  quick-setting  to  allow  of  its  being 
properly  worked.  It  is  therefore  the  general  practice  to  either 
grind  a  small  percentage,  usually  2  or  3  per  cent.,  of  gypsum  with 
the  clinker  or  else  to  add  to  the  cement  just  before  it  is  shipped, 
a  corresponding  percentage  of  finely  ground  plaster  of  Paris,  in 
order  to  regulate  the  set  so  as  to  give  time  for  working,  tamping 
and  troweling.  At  some  mills  coarsely  ground  plaster  of  Paris 
or  calcined  plaster  as  the  manufacturers  call  it,  is  added  to  the 
clinker  before  grinding. 

Le  Chatelier  made  many  experiments  on  the  effect  of  the  addi- 
tion of  gypsum  and  plaster  of  Paris  to  Portland  cement.  He 
concluded  that  the  governing  action  which  it  exercised  over  the 


OF    SETTING  417 

cement  was  due  to  the  formation  of  certain  soluble  compounds 
between  the  sulphuric  acid  of  the  calcium  sulphate  and  the  very 
active  calcium  aluminates  of  the  cement  which  cause  quick-set- 
ting.- He  also  stated  that  either  gypsum  or  plaster  of  Paris  could 
be  added  to  slow  the  set  and  that  the  addition  could  be  made 
either  before  or  after  burning.  Since,  however,  calcium  sulphate 
is  decomposed  at  temperatures  decidedly  below  that  at  which 
Portland  cement  is  burned  there  would  be  a  decided  disadvantage, 
owing  to  loss  of  SO3,  in  adding  gypsum  before  burning.  Indeed 
from  experiments  made  by  the  writer  if  all  the  sulphur  entering 
the  kiln  came  out  with  the  clinker  as  calcium  sulphate  there 
would  be  no  need  to  add  either  gypsum  or  plaster  of  Paris. 

In  spite  of  Le  Chatelier's  experiments,  it  has  been  the  theory 
generally  held  in  this  country  that  gypsum  would  not  retard  the 
set  of  cement,  but  that  the  only  form  of  sulphate  of  lime  which 
would  do  this  is  plaster  of  Paris ;  and  that  where  gypsum  is 
ground  in  with  the  clinker,  this  is  transformed  into  plaster  of 
Paris,  the  heat  generated  during  grinding  being  sufficient  to 
drive  off  the  water  and  make  the  change  from  CaSO4.2H,O  to 
(CaSO4)2H2O.  It  is  true  that  in  many  cases  the  heat  generated 
by  the  friction  of  the  grinding  machinery  is  sufficient  to  drive  off 
the  water,  as  the  writer  has  frequently  tested  cement  fresh  from 
the  tube  mill  and  found  it  over  I3O°C.,  the  temperature  at  which 
gypsum  loses  three-quarters  of  its  water  of  crystallization.  In- 
deed Shenstone  and  Cundall  state  that  gypsum  begins  to  lose  its 
water  of  crystallization  at  70°  C.  in  dry  air. 

To  test  these  various  contrary  theories  and  statements  the 
writer  and  his  assistant,  Mr.  W.  P.  Gano,  carried  out  the  follow- 
ing experiments  i1 

A  sample  of  cement  was  prepared  by  grinding  fresh  normal 
clinker  in  the  usual  way  without  the  addition  of  any  retarder. 
To  separate  portions  of  this  were  added  in  different  percentages 
finely  ground — 

Meade  and  Gano,  Chemical  Engineer,  I,  a,  92. 
27 


4i8 


PORTLAND    CEMENT 


(1)  Plaster   of   Paris,    (CaSO4)2.H2O,   containing   53.18   per 
cent.  SO3. 

(2)  Gypsum  CaSO4.2H2O,  containing  44.22  per  cent.  SO3. 

(3)  Dead  Burned  Gypsum,  CaSO4,  containing  55.21  per  cent. 
S03. 

The  results  are  given  in  the  tables  below: 

The  first  column  shows  the  percentage  of  gypsum,  etc.,  added 
to  the  cement.  By  percentage  is  not  meant  the  percentage  of 
gypsum  in  the  mixture,  but  the  percentage  of  the  weight  of  ce- 
ment of  gypsum  which  is  added.  For  instance,  2  per  cent, 
means  2  grams  of  gypsum  added  to  100  grams  of  cement,  etc. 

The  second  column  shows  the  percentage  of  water  used  for  the 
pat,  being  the  amount  necessary  to  obtain  a  mortar  of  normal 
consistency,  as  determined  by  the  ball  test.  The  third  column 
shows  the  "initial  set"  or  the  time  necessary  for  the  cement  to 
harden  sufficiently  to  bear  the  light  Gilmore  wire,  1/12  inch  in 
diameter,  loaded  with  y±  pound.  The  fourth  column  shows 
the  "final  set"  or  the  time  necessary  for  the  cement  to  harden 
sufficiently  to  bear  the  heavy  Gilmore  wire,  1/24  inch  in  diameter, 
loaded  with  one  pound. 

TABLE  XXXIII.— SHOWING  THE  EFFECT  OF  PLASTER  OF  PARIS  ON  THE 
SETTING  TIME  OF  CEMENT. 


Percentage 
of  Plaster 
of  Paris 
added 

Percentage  of 
water  used  to 
make  pats 

Initial  set 

Final  set 

Hours 

Minutes 

Hours 

Minutes 

0 

25 

O 

2 

o 

6 

0-5 

23 

O 

5 

o 

IO 

I.O 

23 

0 

50 

4 

o 

1-5 

23 

2 

50 

6 

o 

2.0 

22 

3 

o 

6 

15 

3 

22 

I 

45 

5 

20 

4 

22 

0 

35 

4 

O 

5 

22 

0 

16 

2 

0 

10 

22 

0 

16 

I 

30 

20 

22 

O 

9 

O 

20 

TIME    OF    SETTING 


419 


TABLE  XXXIV.— SHOWING  THE  EFFECT  OF  GYPSUM  ON  THE  SETTING 

TIME  OF  CEMENT. 


Percentage 
of 

Percentage 
of  water 

Initial  set 

Final  set 

•SEEP 

used  to 
make  pats 

Hours 

Minutes 

Hours 

Minutes 

I 

23 

O 

2 

0 

10 

2 

23 

2 

40 

5 

50 

3 

22 

2 

50 

5 

50 

5 

22 

3 

15 

6 

00 

10 

22 

3 

O 

5 

40 

20 

22 

3 

20 

6 

00 

Referring  to  the  tables  it  will  be  seen  that  there  is  little  choice 
in  the  three  forms  of  calcium  sulphate  so  far  as  efficiency  goes, 
all  doing  the  work  of  retarding  the  set  about  equally  well.  This 
is  to  be  expected.  If  the  retardation  is  due  to  chemical  action 
there  is  no  reason  why  any  one  of  the  three  forms  should  not  be 
as  efficient  as  the  others,  because  they  all  have  approximately  the 
same  solubility,  that  of  i  part  in  400-500  parts  of  cold  water. 
The  solution  of  any  of  the  four  would  merely  be  one  of  a  mix- 
ture of  two  kinds  of  ions,  CaO  and  SO3,  and  the  SO3  anions 
would  be  as  free  to  react  on  the  aluminates  of  lime  if  their  source 
was  gypsum  as  they  would  if  they  came  from  plaster  of  Paris. 

TABLE  XXXV.— SHOWING  THE  EFFECT  OF  DEAD  BURNED  GYPSUM  ON 
THE  SETTING  TIME  OF  CEMENT. 


Percentage 
of  dead 

Percentage 
of  water 

Initial  set 

Final  set 

burned  gyp- 
sum added 

used  to 
make  pats. 

Hours 

Minutes 

Hours 

Minutes 

I 

23 

O 

6 

O 

IO 

2 

23 

I 

45 

5 

IO 

3 

23 

I 

47 

5 

30 

5 

23 

2 

o 

5 

30 

10 

23 

I 

5o 

5 

o 

20 

23 

2 

20 

5 

o 

It  will  be  noticed,  by  reference  to  Table  XXXIII,  that  2  per 
cent,  plaster  of  Paris  produced  the  maximum  retardation  of  the 
set.  Larger  quantities  than  this  had  the  effect  of  quickening 
the  set  of  the  cement.  This  maximum  of  course  varies  with 
different  cements,  but  with  all  it  will  be  found  that  there  is  a 
point  beyond  which  additions  of  plaster  will  be  attended  with 


420 


PORTLAND   CEMENT 


shortening  instead  of  further  lengthening  the  setting  time  of  the 
cement. 

As  we  have  said  many  manufacturers  prefer  to  add  plaster  of 
Paris  to  cement  just  before  it  is  shipped.  If  it  is  properly  mixed 
with  the  cement  there  are  certainly  points  in  favor  of  adding  the 
sulphate  here.  We  do  not  see,  however,  why  finely  ground  gyp- 
sum would  not  do  the  work  just  as  well,  saving  the  cost  of  cal- 
cining. On  the  other  hand  if  the  gypsum  is  added  to  the  clinker, 
it  is  sure  to  be  finely  ground  and  thoroughly  disseminated 
throughout  the  cement,  two  things  necessary  with  any  form  of 
sulphate,  if  it  is  to  act  as  a  retarder.  There  will  be  no  danger  of 
the  gypsum  failing  to  do  its  work,  whether  the  temperature  is  low 
or  high  during  grinding,  because  dehydration  is  not  necessary. 
It  must  be  remembered,  however,  that  plaster  of  Paris  contains 
more  sulphuric  acid  than  gypsum,  290  parts  of  the  former  being, 
equivalent  to  344  of  the  latter  or  a  ratio  of  87:100  so  that  plaster 
of  Paris  weight  for  weight  is  the  more  effective  of'  the  two. 
Along  this  line,  dead  burned  gypsum  is  still  more  effective  and 
should  be  cheaper  than  plaster  calcined  by  the  kettle  process. 

Influence  of  Calcium  Chl'orlde  on  Setting  Time. 
Another  substance  which  will  retard  the  setting  of  cement  is 
calcium  chloride,  though- the  writer  has  never  heard  of  its  being 
used  in  practice.  Candlot  made  many  experiments  upon  the 
effect  of  chloride  of  calcium  on  the  setting  of  ground  cement 
clinker.  Below  are  some  of  his  results : 

TABLE  XXXVI. — INFLUENCE  OF  CALCIUM  CHLORIDE  ON  THE  SETTING 
TIME  OF  PORTI  AND  CFMENT. 


Solution  of  CaCl2 
Gr.  per  liter 

I 

h.  m. 

2 

h.  m. 

h.  m. 

4 
h.  m. 

2 

0.05 

1.05 

800 

i-34 

5 

0.08 

IO.OO 

12  OO 

2.OO 

10 

8.18 

IO  OO 

I4.OO 

5-50 

20 

I.OO 

12.  OO 

lO.^O 

8.00 

40 

4-35 

800 

6.30 

8.35 

60 

3.20 

6  oo 

4  oo 

6.00 

IOO 

0.03 

O.2O 

o.  30 

3-30 

200 

0.03 

0.09 

0.05 

0.25 

300 

O.O2 

0.08 

0.03 

0.05 

TIME    OF    SETTING 


421 


Carpenter1  also  made  some  experiments  on  grinding  the  clin- 
ker and  calcium  chloride  together.  His  results  are  given  below 
and  show  that  chloride  of  calcium  has  effect  in  retarding  the 
time  if  setting  and  exerts  the  greatest  effect  when  about  one-half 
of  i  per  cent,  by  weight  of  the  chloride  of  calcium  is  employed: 

TABLE  XXXVII.— INFLUENCE  OF  CaCl2  GROUND  DRY  WITH  THE 

CLINKER. 


Per  cent. 
ofCaClo. 

Per  cent, 
of  water 

Initial  set 
minutes 

Final  set 
minutes 

0.0 

29.8 

H5 

274 

0-5 

34-1 

160 

272 

I.o 

29.8 

167 

234 

1,5 

26.4 

127 

212 

2.0 

25-4 

103 

180 

2-5 

26.4 

45 

182 

3-0 

26.4 

97 

185 

3-5 

26.4 

63 

150 

4-5 

28.6 

73 

160 

5-o 

29.8 

76 

84 

5-5 

29.8 

68 

145 

6.0 

29.8 

Effect  of  Storage  of  Portland  Cement  on  Its  Setting  Properties. 

No  property  of  Portland  cement  is  harder  to  control  than  its 
"set,"  or  gives  the  manufacturer  more  trouble.  This  is  not  so 
much  because  of  any  difficulty  in  the  way  of  making  a  slow-set- 
ting cement,  as  it  is  of  making  one  which  will  stay  slow-setting 
under  all  ordinary  conditions  of  storage  and  aging.  Every  manu- 
facturer can  cite  instances  of  cement  which  left  the  mill  having 
the  proper  setting  time,  and  yet  which  turned  up  at  the  job  with 
a  "flash"  set.  Bins  of  freshly  made  cement  will  frequently  test 
slow-setting  and  yet,  after  seasoning  some  weeks,  will  show  quick 
"set  on  again  testing. 

The  converse  of  this  is  also  true,  some  cements  which,  when 
freshly  made  are  quick-setting,  will  in  time  become  slow-setting, 
and  again  slow-setting  cements  may  become  quick-setting  and 
then  slow-setting  again.  /As  a  usual  rule  a  cement  which  is  slow- 
setting  when  freshly  made  and  which  becomes  quick-setting  on 

1  Sibley,  Journal  of  Engineering,  (Cornell  University)  January,  1905. 


422 


PORTLAND    CE)ME)NT 


storage  is  under-limed,  and  the  trouble  can  usually  be  remedied 
by  increasing  the  percentage  of  lime  in  the  cement.  High-limed, 
well-burned  and  made  cements  do  not  usually  show  this  fault. 
What  percentage  of  lime  it  is  necessary  to  carry  in  order  to 
avoid  this  trouble  is  a  question  every  mill  must  decide  for  itself, 
but,  in  general,  it  may  be  said  that  cements  high  in  alumina  will 
require  a  high  percentage  of  lime  to  overcome  this  fault,  and  in 
some  instances  the  margin  between  the  minimum  of  lime  to  in- 
sure against  quick  set  and  the  maximum  allowed  by  a  good  hot 
test  is  very  narrow. 

J  The  table  below  illustrates  the  changes  in  the  setting  time  of 
cement,  due  to  aging. 

TABLE  XXXVIII. — INFLUENCE  OF  AGING  ON  THE  SET  OF  PORTLAND 

CEMENT. 


i 

2 

3 

4 

5 

6 

7 

H 

M 

H 

M 

H 

M 

H 

M 

H 

M 

H 

M 

H 

M 

Fresh 

Initial  set 
Final  set 

2 

6 

50 
O 

3 
6 

10 

40 

4 
8 

10 
0 

2 
6 

40 

1,5 

2 

TS 

IO 
25 

4 

10 

i  week  old  •  •  • 

Initial  set 
Final  set 

i 

4 

3° 

10 

10 

25 

2 

6 

15 

0 

i 

2 

TO 

5 
15 

4 

IO 

2  weeks  old  .  • 

Initial  set 
Final  set 

o 
o 

3 
7 

5 
ii 

I 
3 

25 
40 

i 

15 

^5 

I 

30 
5 

4 

10 

4  weeks  old  •  • 

Initial  set 
Final  set 

o 

0 

3 

7 

5 
15 

i 

30 
50 

5 
ii 

I 

4 

30 

10 

I 

4 

50 

45 

15 
30 

3  months  old  . 

Initial  set 
Final  set 

I 

30 
15 

4 
15 

; 

IO 

30 

3 
8 

i 
4 

35 

0 

2 

6 

o 

IO 

2 

6 

40 

5 

6  months  old  • 

Initial  set 
Final  set 

I 

25 
i,5 

i° 

20 

10° 

•' 

8 

2 

6 

10 

o 

2 

6 

o 

IO 

2 

5 

IO 

40 

i  year  old  

Initial  set 
Final  set 

I 

25 

10 

2 

55 
30 

2 

5 

20 

45 

4 

10 

2 

5 

o 

30 

I 
5 

40 

5 

2 

6 

15 
5 

The  reason  commonly  given  for  the  quickening  of  the  set  of 
Portland  cement  is  that  the  plaster  of  Paris  (CaSO4)2H2O,  has 
hydrated  and  reverted  to  gypsum,  CaSO4.2H2O.  It  is  a  fact, 
however,  as  is  generally  well  known,  and  as  we  have  mentioned 
before  that  gypsum  is  practically  as  efficacious  a  retarder  as 
plaster  of  Paris.  Not  only  will  trie  mineral  gypsum  slow  the  set 
of  cement  but  the  artificial  gypsum,  formed  when  plaster  hydrates 


TIME    OF    SETTING 


423 


or  sets,  will  also  act  in  the  same  manner,  as  the  following  re- 
sults will  show. 

TABLE  XXXIX.— THE  EFFECT  OF  "SET"  PIASTER  OF  PARIS  ON  THE 
SETTING  TIME  OF  CEMENT. 


Percentage  of 
"  set  "  plaster 
of  Paris  added 

Percentage  of 
water  used  to 
make  pats 

Initial  set 

Final  set 

Hours 

Minutes 

Hours 

Minutes 

O 

25 

O 

2 

O 

6 

I 

23 

O 

8 

O 

40 

2 

23 

I 

45 

5 

0 

3 

23 

2 

O 

5 

20 

5 

23 

I 

45 

6 

O 

10 

23 

I 

55 

5 

35 

20 

23 

2 

15 

5 

50 

In  view  of  the  fact  that  both  gypsum  and  set  plaster  of  Paris, 
which  is  merely  plaster  of  Paris  reverted  into  gypsum,  will  slow 
the  set  of  cement,  there  can  be  nothing  in  the  theory  that  plaster 
loses  in  time  its  control,  over  cement,  for  the  only  change  which 
,the  plaster  can  undergo  is  to  absorb  water  from  the  air  forming 
gypsum.  We  must  therefore  seek  for  another  solution  of  the 
matter.  Mr.  Clifford  Richardson  suggested  one,  in  his  paper  on 
the  "Constitution  of  Portland  Cement,"  read  before  the  Associa- 
tion of  Portland  Cement  Manufacturers,  at  Atlantic  City,  June, 
1904.  His  theory  being  that  the  tension  in  the  solid  solution  of 
calcium  silicates  and  aluminates,  which  constitutes  cement,  is  re- 
leased by  changes  in  temperature,  etc.,  setting  free  some  alumi- 
nate  which  makes  the  cement  quick-setting  again. 

Against  this  latter  theory  are  several  facts,  chief  of  which  is 
that  cements  kept  in  air-tight  vessels  do  not  get  quick-setting. 
The  writer  has  many  times  divided  a  sample  of  cement,  which 
from  its  analysis  led  him  to  believe  it  would  develop  a  "flash" 
set  on  aging,  into  two  portions,  storing  one  in  a  small  paper  bag 
and  the  other  in  an  air-tight  fruit  jar,  and,  in  no  case,  has  he  ever 
observed  the  sample  in  the  jar  to  become  quick-setting,  although! 
in  most  cases  that  in  the  bag  developed  an  initial  set  of  from 
2  to  10  minutes  after  a  week's  time.  In  making  this  test  three 
pats  were  always  made  of  each  sample,  both  before  and  after 


424  PORTLAND    CEMENT 

aging,  and  the  bag  and  jar  were  placed  side  by  side  on  the  shelf, 
where  both  would  be  subjected  to  the  same  changes  of  tem- 
perature, etc. 

v  Influence  of  Slaked  Lime  on  Setting  Time. 

When  cement  has  become  quick-setting  from  storage  it  can 
generally  be  made  slow-setting  again  by  simply  adding  I  or  2 
per  cent,  of  slaked  lime,  or  by  gauging  the  pat  with  lime-water. 
This  seems  toTead~To  the  conclusion  advanced  by  Candlot  that 
the  quickening  of  the  set  of  cement  on  exposure  to  air  is  due  to 
the  change  of  the  small  percentage  of  free  or  of  hydrated  lime  al- 
ways present  in  cement  to  the  inert  carbonate.  This  change  is 
brought  about  by  the  carbon  dioxide  of  the  air,  consequently, 
when  not  exposed  to  the  air,  the  cement  does  not  become  quick- 
setting.  Slaked  lime  will  not  itself  slow  the  setting  of  urisul- 
phated  cement,  and  calcium  sulphate  must  be  present  in  some 
form  or  other,  so  that  it  is  probably  a  mixture  of  calcium  sul- 
phate and  calcium  hydrate  which  retards  the  hydration  of  the 
aluminates,  and  consequently  the  activity  of  the  cement. 

Cement  which  has  become  quick-setting  may  also  be  made 
slow-setting  again  by  addition  of  a  small  percentage  of  plaster 
of  Paris.  One-half  of  one  per  cent,  is  usually  sufficient  for  this 
purpose.  When  bins  of  cement  have  become  quick-setting,  from 
age,  it  is  usual  to  bring  the  setting  time  back  to  normal  by  such 
means.  Usually  a  square  box  made  to  hold  so  much  plaster 
of  Paris  (when  struck  off  level)  is  added  to  every  barrow  of  ce- 
ment as  it  is  wheeled  from  the  bin  to  the  conveyor,  or  else  a  box 
is  dumped  into  the  conveyor  at  stated  intervals  of  time.  The 
screw  conveyor  then  does  the  mixing  and  usually  does  it  pretty 
thoroughly,  too.  Some  mills  are  provided  with  automatic  scales 
and  mixers  for  doing  this  work,  but  these  are  usually  installed 
only  in  those  mills  which  use  plaster  of  Paris  and  make  the 
addition  before  packing,  instead  of  grinding  gypsum  in  with  the 
clinker. 

Quick-setting  cements  may  also  be  rendered  slow-setting  by 
mixing  them  with  slow-setting  ones,  but  this  must  be  carefully 


OF    SETTING  425 

done  to  see  that  both  bins  are  drawn  from  in  the  desired  propor- 
tions. 

(The  property  slaked-lime  has  of  slowing  the  setting  time  of 
cement  which  has  quickened  with  age  does  not  seem  to  be  utilized 
as  much  as  it  might  be.y  I  know  of  one  cement  mill  where  slaked 
lime  was  added  for  a  short  time  for  this  purpose  and  of  another 
which  contemplated  doing  so.  Most  manufacturers,  however, 
have  found  it  simpler  to  add  a  little  more  plaster  of  Paris  to  such 
cement  as  becomes  quick-setting,  just  before  it  is  packed  and  so 
bring  back  its  setting  time  to  the  normal.  The  contractor  or 
engineer,  however,  might  in  many  cases  add  slaked  lime  to  the 
cement  and  so  relieve  the  manufacturer  of  the  expense  of  taking 
the  cement  back  to  the  mill  in  order  to  plaster  it.  On  small  jobs, 
where  water  is  added  to  the  concrete  from  barrels,  the  addition 
of  a  few  lumps  of  lime  to  the  contents  of  the  barrel  would  make 
the  cement  slow-setting,  and  the  resulting  concrete  would  be  as 
strong  as  if  no  lime  had  been  added.  Sidewalk  makers  and  other 
users  of  cement  who  do  not  test  their  purchases  may  safeguard 
themselves  against  using  quick-setting  cement  unawares  by  the 
use  of  lime  in  this  way  or  by  mixing  hydrated  lime  with  the 
mortar. 

V  Influence  of  Chemical  Composition  on  Setting   Tiiitf. 

The  influence  of  chemical  composition  on  the  setting  time  of 
Portland  cement  has  been  gone  into  to  some  extent  in  the  sec- 
tions on  "lime,"  "alumina"  and  "silica"  in  Chapter  II  and  need 
not  be  repeated  here. 


Chapter  XVII. 


TENSILE  STRENGTH. 


STANDARD  SPECIFICATIONS. 


Specification. — The  minimum  requirements  for  tensile  strength 
for  briquettes  one  inch  square  in  section  shall  be  within  the  fol- 
lowing limits,  and  shall  show  no  retrogression  in  strength  within 
the  periods  specified: 

Age                                       Neat  cement  Strength 

24  hours  in  moist  air 175  pounds 

7  days  (i  day  in  moist  air,  6  days  in  water) 500  pounds 

28  days  ( i  day  in  moist  air,  6  days  in  water) 600  pounds 

One  part  cement,  three  parts  standard  Ottawa  sand 

7  days  ( i  day  in  moist  air,  6  days  in  water) 200  pounds 

28  days  ( i  day  in  moist  air,  6  days  in  water) 275  pounds 

METHOD  OF  OPERATING  THE  TEST. 

t 

Standard  Sand. 

For  the  present,  the  committee  recommends  the  natural  sand 
from  Ottawa,  HI.,  screened  to  pass  a  sieve  having  20  meshes  per 
linear  inch  and  retained  on  a  sieve  having  30  meshes  per  linear 
inch;  the  wires  to  have  diameters  of  0.0165  and  0.0112  in.,  re- 
spectively, i.  e.,  half  the  width  of  the  opening  in  each  case.  Sand 
having  passed  the  No.  20  sieve  shall  be  considered  standard  when 
not  more  than,  i  per  cent,  passes  a  No.  30  sieve  after  one  minute 
continuous  sifting  of  a  500  gram  sample. 

Form  of  Briquette. 

While  the  form  of  the  briquette  recommended  by  a  former 
committee  of  the  Society  is  not  wholly  satisfactory,  this  committee 
is  not  prepared  to  suggest  any  change,  other  than  rounding  off 
the  corners  by  curves  of  J/£  in.  radius,  Fig.  134. 


STRENGTH 


427 


Molds. 


The  molds  should  be  made  of  brass,  bronze  or  some  equally 
non-corrodible  material,  having  sufficient  metal  in  the  sides  to 
prevent  spreading  during  molding. 

Gang  molds,  which  permit  molding  a  number  of  briquettes  at 


Fig.  134. — Standard  form  of  briquette. 

one  time,  are  preferred  by  many  to  single  molds ;  since  the  great- 
er quantity  of  mortar  that  can  be  mixed  tends  to  produce  greater 
uniformity  in  the  results.  The  type  shown  in  Fig.  135  is  recom- 
mended. 

The  molds  should  be  wiped  with  an  oily  cloth  before  using. 


428  PORTLAND    CEMENT 

Mixing. 

All  proportions  should  be  stated  by  weight;  the  quantity  of 
water  to  be  used  should  be  stated  as  a  percentage  of  the  dry 
material. 

The  metric  system  is  recommended  because  of  the  convenient 
relation  of  the  gram  and  the  cubic  centimeter. 

The  temperature  of  the  room  and  the  mixing  water  should  be 
as  near  21°  C.  (70°  F.)  as  it  is  practicable  to  maintain  it. 


i  i 


Fig.  135. — Gang  mold,  lever  clamp. 

The  sand  and  cement  should  be  thoroughly  mixed  dry.  The 
mixing  should  be  done  on  some  non-absorbing  surface,  prefera- 
bly plate-glass.  If  the  mixing  must  be  done  on  an  absorbing  sur- 
face it  should  be  thoroughly  dampened  prior  to  use. 

The  quantity  of  material  to  be  mixed  at  one  time  depends  on 
the  number  of  test  pieces  to  be  made;  about  1,000  gr.  (35.28  oz.) 
makes  a  convenient  quantity  to  mix,  especially  by  hand  methods. 

Method. — The  material  is  weighed  and  placed  on  the  mixing 
table,  and  a  crater  formed  in  the  center,  into  which  the 
proper  percentage  of  clean  water  is  poured ;  the  material  on  the 
outer  edge  is  turned  into  the  crater  by  the  aid  of  a  trowel.  As 
soon  as  the  water  has  been  absorbed,  which  should  not  require 
more  than  one  minute,  the  operation  is  completed  by  vigorously 
kneading  with  the  hands  for  an  additional  I1/*  minutes,  the  pro- 
cess being  similar  to  that  used  in  kneading  dough.  A  sand-glass 
affords  a  convenient  guide  for  the  time  of  kneading.  During  the 
operation  of  mixing,  the  hands  should  be  protected  by  gloves, 
preferably  of  rubber. 

Molding. 

Having  worked  the  paste  or  -mortar  to  the  proper  consistency 
it  is  at  once  placed  in  the  molds  by  hand. 


TENSILE    STRENGTH  429 

Method. — The  molds  should  be  filled  at  once,  the  material 
pressed  in  firmly  with  the  fingers  and  smoothed  off  with  a  trowel 
without  ramming :  the  material  should  be  heaped  up  on  the  upper 
surface  of  the  mold,  and,  in  smoothing  off,  the  trowel  should  be 
drawn  over  the  mold  in  such  a  manner  as  to  exert  a  moderate 
pressure  on  the  excess  material.  The  mold  should  be  turned 
over  and  the  operation  repeated. 

A  check  upon  the  uniformity  of  the  mixing  and  molding  is  af- 
forded by  weighing  the  briquettes  just  prior  to  immersion,  or 
upon  removal  from  the  moist  closet.  Briquettes  which  vary  in 
weight  more  than  3  per  cent,  from  the  average  should  not  be 
tested. 

Storage  of  the  Test  Pieces. 

During  the  first  24  hours  after  molding  the  test  pieces  should 
be  kept  in  moist  air  to  prevent  them  from  drying  out. 

A  moist  closet  or  chamber  is  so  easily  devised  that  the  use  of 
the  damp  cloth  should  be  abandoned  if  possible.  Covering  the 
test  pieces  with  a  damp  cloth  is  objectionable,  as  commonly  used, 
because  the  cloth  may  dry  unequally,  and  in  consequence  the 
test  pieces  are  not  all  maintained  under  the  same  conditions. 
Where  a  moist  closet  is  not  available,  a  cloth  may  be  used  and 
kept  uniformly  wet  by  immersing  the  ends  in  water.  It  should 
be  kept  from  direct  contact  with  the  test  pieces  by  means  of  a 
wire  screen  or  some  similar  arrangement. 

A  moist  closet  consists  of  a  soapstone  or  slate  box,  or  a  metal- 
lined  wooden  box — the  metal  lining  being  covered  with  felt  and 
this  felt  kept  wet.  The  bottom  of  the  box  is  so  constructed  as  to 
hold  water,  and  the  sides  are  provided  with  cleats  for  holding 
glass  shelves  on  which  to  place  briquettes.  Care  should  be 
taken  to  keep  the  air  in  the  closet  uniformly  moist.  (Refer  to 
Chapter  XVI.) 

After  24  hours  in  moist  air  the  test  pieces  for  longer  periods  of 
time  should  be  immersed  in  water  maintained  as  near  21°  Cent. 
(70°  Fahr.)  as  practicable;  they  may  be  stored  in  tanks  or  pans, 
which  should  be  of  non-corrodible  material. 


430 


PORTLAND 


Tensile  Strength. 

The  tests  may  be  made  on  any  standard  machine.  A  solid 
metal  clip,  as  shown  in  Fig.  136,  is  recommended.  This  clip  is  to 
be  used  without  cushioning  at  the  points  of  contact  with  the  test 
specimen.  The  bearing  at  each  point  of  contact  should  be  J4  m- 
wide,  and  the  distance  between  the  center  of  contact  on  the  same 
clip  should  be  1^4  ms- 
TABLE  XL. — PERCENTAGE  OF  WATER  FOR  STANDARD  SAND  MORTARS. 


One  cement 

One  cement 

One  cement 

Neat 

three  standard 

Neat. 

three  standard 

Neat 

three  standard 

Ottawa  sand 

Ottawa  sand 

Ottawa  sand 

15 

8.0 

23 

9-3 

31 

10.7 

16 

8.2 

24 

9-5 

32 

10.8 

I? 

8-3 

25 

9-7 

33 

II.  0 

18 

8.5 

26 

9.8 

34 

II.  2 

19 

8-7 

27 

10.0 

35 

II-5 

20 

8.8 

28 

10.2 

36 

"•5 

21 

9.0 

29 

10.3 

37 

11.7 

22 

9.2 

3° 

10.5 

38 

n.8 

I   tO   I 

I   tO  2 

i  to  3 

i  to  4 

i  to  5 

Cement  •  •  • 

500 

333 

250 

2OO 

I67 

Sand  

500 

666 

750 

800 

833 

Test  pieces  should  be  broken  as  soon  as  they  are  removed 
from  the  water.  Care  should  be  observed  in  centering  the  bri- 
quettes in  testing  machine,  as  cross-strains,  produced  by  im- 
proper centering,  tend  to  lower  the  breaking  strength.  The  load 
should  not  be  applied  too  suddenly,  as  it  may  produce  vibration, 
the  shock  from  which  often  breaks  the  briquettes  before  the  ulti- 
mate strength  is  reached.  Care  must  be  taken  that  the  clips  and 
the  sides  of  the  briquette  be  clean  and  free  from  grains  of  sand 
or  dirt,  which  would  prevent  a  good  bearing.  The  load  should  be 
applied  at  the  rate  of  600  Ibs.  per  minute.  The  average  of  the 
briquettes  of  each  sample  tested  should  be  taken  as  the  test,  ex- 
cluding any  results  which  are  manifestly  faulty. 

NOTES. 
The  British  standard  specifications  use  the  same  form  of  bri- 


STRENGTH 


quette  as  that  prescribed  by  the  American  rules.  The  specifi- 
cations, however,  as  to  tensile  strength  differ  somewhat  from 
the  American  requirements  in  that  they  specify  a  definite  increase 


Fig.  136.— Standard  form  of  clip. 

between  the  7  and  28  day  periods.    The  specifications  are  as 
follows : 

7  days  from  gauging. . .  .400  Ibs.  per  square  inch  of  section. 

28  days  from  gauging. . .  .500  Ibs.  per  square  inch  of  section. 

The  increase  from  7  to  28  days  shall  not  be  less  than : — 

25  per  cent,  when  the  7  day  test  falls  between  400  Ibs.  to  450 
Ibs.  per  square  inch  of  section. 

20  per  cent,  when  the  7  day  test  falls  between  450  Ibs.  to  500 
Ibs.  per  square  inch  of  section. 

15  per  cent,  when  the  7  day  test  falls  between  500  Ibs.  to  550 
Ibs.  per  square  inch  section. 

10  per  cent,  when  the  7  day  test  is  550  Ibs.  per  square  inch 
or  upwards. 

When  tested  with  a  natural   sand   from   Leighton   Buzzard, 


PORTLAND    CEMENT 

sized  to  pass  a  No.  20  and  be  retained  or  a  No.  30,  in  the  pro- 
portions of  one  part  cement  to  three  of  sand,  the  requirements 
are: — 

7  days  from  gauging.  . .  .120  Ibs.  per  square  inch  of  section. 
28  days  from  gauging.  .  .  .225  Ibs.  per  square  inch  of  section. 

Standard  Sand. 

Up  to  the  adoption  of  the  above  standard  rules,  crushed  quartz 
such  as  is  used  in  the  manufacture  of  sandpaper,  was  considered 
the  standard  sand,  having  been  recommended  by  a  former  com- 
mittee of  the  American  Society  of  Civil  Engineers.  Indeed,  it  is 
probable  that  it  is  still  used  in  by  far  the  greater  number  of  test- 
ing laboratories  in  the  country.  As  this  sand  is  a  commercial 
product  it  can  be  obtained  in  large  quantities  and  of  standard 
grades.  The  crushed  quartz  should  be  of  such  size  that  it 
will  all  pass  a  No.  20  sieve  and  yet  be  retained  upon  a  No.  30. 

Where  the  value  of  the  cement  is  desired  with  regard  to  some 
particular  piece  of  work,  the  sand  used  for  the  test  may  be  the 
sand  that  is  to  be  used  for  the  work.  In  this  case  it  is  the  mortar 
that  is  tested  rather  than  the  cement.  Just  as  a  series  of  tests 
made  with  a  standard  sand  and  various  brands  of  cement  would 
give  the  comparative  value  of  the  cements,  so  a  series  of  tests 
with  an  established  brand  of  cement  and  various  sands  will  give 
the  comparative  value  of  the  sands. 

Cement,  when  tested  with  the  natural  Ottawa  sand,  usually 
shows  a  greater  strength  than  when  tested  with  crushed  quartz. 
In  the  case  of  7  day  breaks,  the  higher  figure  may  be  as  much  as 
40  per  cent,  of  the  lower.  The  reason1  for  this  difference  is  due 
to  the  shape  of  the  sand  grains.  The  Ottawa  sand  being  round,  it 
compacts  much  more  closely  and  has  a  lower  percentage  of  voids 
than  crushed  quartz,  as  the  latter  has  sharp  and  angular  grains, 
which  mass  and  wedge,  leaving  more  space  between  the  sand 
particles. 

Other  Forms  of  Briquettes. 

Fig.  137  shows  the  form  of  briquette  recommended  in  the  re- 
port of  a  former  committee  on  a  uniform  system  for  tests  of 

1  Brown,  Proceedings  of  Am.  Soc.  for  Test.  Mat.,  IV.,  (1904),  124. 


TENSILE    STRENGTH 


433 


cement  of  the  American  Society  of  Civil  Engineers,1  which  is 
similar  to  the  present  standard  except  that  the  latter  has  round- 
ed corners.  Fig.  138  shows  the  form  recommended  by  the  As- 
sociation of  German  Cement  Makers,  which  is  the  standard 
in  Germany.  The  dimensions  of  the  two  forms  are  given  in 


Fig.  137. — Old  standard 
form  of  briquette. 


Fig.  138.— German  standard 
form  of  briquette. 


the  drawings.  As  will  be  seen,  the  weakest  section  of  bri- 
quettes of  either  form  is  at  the  center  and  is  one  inch  in  cross- 
section,  in  the  case  of  the  United  States  standard;  and  5  square 
centimeters  in  that  of  the  German.  Comparative  tests  show 
the  American  standard  to  give  the  higher  result  of  the  two.  In 
the  case  of  briquettes  of  neat  cement,  this  difference  amounts 
sometimes  to  as  much  as  30  or  40  per  cent,  of  the  lower. 

The  briquettes  to  be  broken  at  the  expiration  of  twenty-four 
hours  are  made  of  neat  cement,  that  is,  cement  alone,  while 
those  to  be  broken  only  after  the  lapse  of  seven  days  or  longer, 
should  be  made  both  of  neat  cement  and  of  a  mixture  of  one 
part  cement  to  three  parts  sand. 

Molds. 

Other  types  of  briquette  molds  are  shown  in  Fig.  139.  The 
first  of  these  is  held  together  by  a  clamp  provided  with  a  thumb 
screw  but  in  the  writer's  opinion  has  no  advantage  over  the  stand- 
ard form  and  the  disadvantage  of  an  extra  part.  The  second 
mold  shown  is  made  by  the  Humbolt  Mfg.  Co.,  Chicago.  The 

1  This  committee  presented  its  report  at  the  annual  meeting  of  the  society,  January. 
21,  1885,  and  was  then  discharged. 
28 


43- 


PORTXAND 


clamp  is  provided  with  an  excentric  bearing  so  that  when  it  is 
revolved  in  a  half  circle,  or  over  to  the  other  side  from  that 
shown,  the  two  halves  of  the  mold  are  separated,  thus  facilitat- 
ing the  removal  of  the  briquettes. 

Molds  are  usually  made  of  gun-metal,  brass,  bronze  or  some 
alloy  of  copper  which  does  not  rust  on  exposure  to  moisture 


Fig.  139. — Other  forms  of  briquette  molds. 

Mr.  Force,  Engineer  of  Tests  of  the  Lackawanna  R.  R.,  tried 
aluminum  molds  but  found  that  while  they  were  light  and  stiff 
enough,  the  test-pieces  stuck  to  them  badly. 

Fig.  140  shows  another  form  of  gang  mold.  If  a  hole  is  bored 
through  from  side  to  side  of  this  mold,  between  the  third  and 
fourth  openings,  so  as  not  to  interfere  with  the  briquettes,  and 
a  bolt  provided  with  a  thumb-screw  is  run  through  this,  the 
mold  will  be  considerably  stiffened  thereby  and  springing  will 
be  guarded  against. 


Fig.  140. — Gang  mold,  adjustable  lever  clamp. 

To  clean  the  molds,  lay  them  all  flat  on  the  table  without  the 
clamps  just  as  if  briquettes  were  to  be  made  and  scrape  off  any 
hardened  cement  with  a  piece  of  sheet  zinc  or  other  soft  metal. 
Then  brush  off  with  a  stiff  bristle  brush  and  wipe  with  a  piece 
of  oily  waste.  Turn  the  molds  over  and  repeat  the  process  on 
the  other  face.  Now  separate  the  molds  and  place  the  halves 


STRENGTH 


435 


in  a  long  line  with  the  mold  part  forming  a  trough,  brush  with 
a  stiff  brush  and  wipe  off  with  oily  waste.  Briquettes  should 
not  be  allowed  to  become  too  hard  before  removing  from  the 
molds.  For  most  cements,  if  briquettes  are  made  in  the  morn- 
ing, they  can  be  removed  from  the  molds  in  the  afternoon,  and 
the  molds  cleaned  at  once  before  the  cement  hardens. 


G 


Fig.  141.— Scraper  for  cleaning  molds. 

Fig.  141  shows  a  scraper  for  cleaning  molds.  This  consists  of 
a  block  of  wood  5X3  inches,  rounded  to  form  a  handle,  into 
which  is  fixed  a  piece  of  zinc. 

Mixing. 

In  place  of  a  glass  plate,  a  sheet  of  brass  ^-inch  thick  makes 
an  excellent  mixing  surface.  Slate  and  soapstone  slabs  are  also 
used.  Both,  however,  absorb  water  and  draw  it  away  from  the 
briquettes.  This  can  be  avoided  by  keeping  a  damp  cloth  over 
that  part  of  the  table  used  for  mixing  when  not  in  service.  Or 
melted  paraffine  may  be  poured  over  the  heated  slab  and  allowed 
to  soak  in  and  the  whole  then  cooled.  The  excess  of  paraffine  is, 
of  course,  to  be  scraped  off  with  a  metal  scraper. 

Fig.  142  shows  a  convenient  table  for  mixing  mortar  and  mak- 
ing briquettes  and  pats.  It  consists  of  a  table  arranged  with 
glass  or  brass  plates  or  slate  slabs  at  either  end  and  the  central 
part  of  the  table  raised  four  or  five  inches  above  the  ends  as 
shown.  The  space  between  the  shelf  and  the  glass  plate  is  left 
open  so  that  the  surplus  mortar,  etc.,  used  in  making  a  set  of 
briquettes  may  be  swept  through  this  and  into  a  waste  can  placed 
below.  A  piece  of  tin  bent  to  form  a  trough,  as  shown,  con- 
ducts the  waste  into  the  can.  Above  the  first  shelf,  which  is 


436 


PORTLAND  CEMENT 


used  for  the  scales,  measuring  cylinders,  pat  glasses,  etc.,  a 
second  shelf  is  supported  by  four  uprights — one  at  each  corner. 
At  each  end  of  this  shelf  are  to  be  placed  2  gallon  bottles  pro- 
vided with  siphons  of  glass  and  rubber  as  shown.  These  si- 
phons are  closed  by  pinch-cocks,  as  shown.  Drawers  may  be 


r 


00       Waste  B  > 

Can 


J         L 


n — n 


Fig.  142. — Table  for  mixing  mortar  and  making  briquettes  and  pats. 

placed  in  front  of  the  table  for  holding  such  articles  as  trowels, 
spatulas,  etc.  Four  2-gallon  bottles  should  be  provided,  and 
while  two  are  in  use  on  the  table  the  other  two  should  be  full 
and  standing  nearby  to  get  the  room  temperature. 

Instead  of  kneading  the  cement  mortar  with  the  hands  as 
prescribed  by  the  standard  rules,  the  larger  number  of  testers 
use  a  trowel,  working  the  mortar  back  and  forth  on  the  table, 
under  the  trowel. 

Percentage  of  Water. 

The  percentage  of  water  used  in  gauging  the  mortar  for  the 
test  pieces  has  a  considerable  influence  on  the  strength  of  the 


STRENGTH 


437 


cement.     This  is  shown  by  the  table  given  below  which  is  taken 

TABLE  XLI.— INFLUENCE  OF  VARIOUS  PROPORTIONS  OF  WATER  ON 
THE  NEAT  STRENGTH  OF  PORTLAND  CEMENT.    (E.  S.  LARNED.  ) 


Tensile  strength 

Water 

brand 

per  cent. 

24 

7 

28 

3 

6 

12 

hours 

days 

days 

months 

months 

months 

15 

371 

655 

875 

941 

720 

787 

16 

3°3 

750 

973 

I008 

735 

816 

Giant 

18 

260 

649 

773 

831 

645 

748 

Portland 

20 

233 

500 

693 

716 

62! 

6;6 

22 

184 

546 

636 

658 

601 

589 

24 

167 

539 

649 

644 

629 

755 

13 

366 

775 

859 

1067 

892 

832 

14 

404 

780 

891 

972 

852 

78i 

Atlas 
Portland 

16 
18 

20 

308 
225 

602 
570 
59° 

725 
723 
7i8 

844 
785 
76o 

806 
728 
6.4 

723 
724 
636 

22 

116 

554 

649 

73  1 

643 

604 

24 

42 

5io 

691 

695 

632 

574 

from  a  paper  by  Mr.  E.  S.  Larned1  on  this  subject.  It  will  be 
noticed  that  in  the  case  of  both  cements,  the  dryer  mixtures  give 
the  higher  results.  This  is  probably  due  to  the  fact  that  the  dry 
mixtures  require  hammering  or  ramming  to  get  them  in  the 
molds,  while  the  wet  mixtures  were  merely  forced  in  with  the 
thumb  as  they  were  too  soft  for  this  treatment.  Other  experi- 
menters, however,  have  found  results  differing  in  some  particu- 
lars from  Mr.  Larned,  and  while  agreeing  with  him  that  the 
dryer  mixtures  give  higher  short  time  tests,  their  experiments 
show  the  differences  on  long  time  tests  to  be  slight  and  usually 
in  favor  of  the  wet  mixtures.  This  has  also  been  the  writer's 
experience,  but  in  his  case  both  the  dry  and  the  wet  mixtures 
were  merely  pressed  into  the  molds  with  the  thumbs. 

Storage  of  Briquettes. 

The  briquettes  may  be  placed  in  water  either  flat  or  on  edge. 
The  latter  gives  more  surface  exposed  to  the  water.  The  tanks 
in  which  the  briquettes  are  immersed  may  be  made  of  galvanized 

»  Proceedings,  Amer.  Soc.  Test.  Mat.,  III.,  (1903),  401. 


438  PORTLAND    CEMENT 

iron  and  of  any  desired  size.  They  are  usually,  however,  from 
two  to  six  inches  deep.  Where  space  i-s  limited,  they  may  be 
placed  one  above  the  other  on  a  suitable  framework. 

When  much  testing  has  to  be  done,  a  good  form  of  trough 
for  the  storage  of  briquettes  is  made  of  stout  two-inch  board 
lined  with  sheet  zinc.  These  troughs  may  be  placed  one  above 
the  other  on  a  suitable  wood  frame.  A  small  stream  of  water 
should  be  kept  running  through  them  all  the  time.  This  can  be 
done  by  arranging  overflow  tubes  so  that  the  water  will  flow 
from  the  upper  trough  into  the  next  one  below,  etc. 

In  the  writer's  laboratory,  the  briquette  trough  is  placed  in 


Fig.  143. — Marked  briquette. 

the  cellar  and  is  made  of  concrete.  It  is  raised  about  2  feet 
from  the  floor  and  is  8  inches  deep.  The  water  level  is  main- 
tained at  about  6  inches.  The  temperature  of  this  cellar  is  very 
even  both  in  summer  and  winter.  In  making  the  trough,  a  very 
dense  concrete  was  used  so  as  to  be  sure  of  no  leakage  from  it 
into  the  cellar. 

After  the  briquettes  have  attained  their  initial  set  they  should 
be  marked  with  an  identifying  number  by  a  steel  die  and  dated 
as  shown  in  Fig.  143.  The  marking  should  always  be  done  in  the 
corners  and  never  across  the  breaking  section.  Sand  briquettes 
may  be  marked  by  putting  a  thin  layer  of  neat  cement  about 
1/1.6  inch  thick  on  one  end  and  marking  this.  The  usual  plan, 
however,  is  only  to  mark  the  neat  briquettes  and  store  the  sand 
briquettes  with  these,  in  the  trough,  in  such  a  manner  as  to  make 
identification  possible.  When  briquettes  are  only  to  be  made  for 


STRENGTH  439 

short  periods  a  pencil  may  be  used  for  marking,  but  where  long 
time  tests  are  made  steel  dies  should  be  used. 

In  storing  the  briquettes  in  the  troughs,  it  will  be  found  most 
convenient  to  put  all  the  briquettes  to  be  broken  in  7  days,  in 
order  of  making,  in  one  part  of  the  trough,  and  those  for  28 
days  in  another,  etc.  The  briquettes  may  be  placed  edgewise, 
in  pairs,  one  on  top  of  the  other ;  and  where  the  sand  briquettes 
are  not  marked,  it  will  be  found  a  good  plan  to  place  the  neat 
briquettes  over  the  corresponding  sand  ones. 

The  number  of  briquettes  to  be  made,  and  the  time  when  these 
are  to  be  broken,  will  vary  with  circumstances.  Usually,  in  per- 
manent laboratories,  briquettes  are  made  to  be  broken  at  periods 
of  24  hours,  7  days,  28  days,  3  months,  6  months,  i  year,  2  years, 
5  years  and  10  years.  Usually  from  3  to  5  briquettes,  both  sand 
and  neat,  are  broken  at  each  period,  except  at  24  hours,  when 
only  neat  briquettes  are  broken.  In  temporary  laboratories,  how- 
ever, the  long  time  tests  are,  of  course,  omitted.  Three  neat 
and  three  sand  briquettes  are  usually  considered  enough  to  test 
the  strength  of  cement  at  any  period,  though  in  some  labora- 
tories only  two  of  each  kind  are  broken. 

The  briquettes  should  always  be  put  in  the  testing  machine 
and  broken  immediately  after  being  taken  out  of  the  water,  and 
the  temperature  of  the  briquette  and  of  the  testing  room  should: 
be  constant,  between  60°  and  70°  F.  Seven  days  neat  briquettes- 
kept  in  the  room  and  allowed  to  dry  out  for  24  hours  before 
breaking,  in  many  instances,  break  at  less  than  half  the  strain 
of  those  kept  in  water  the  full  period.  Sand  briquettes,  how- 
ever, seldom  show  any  very  marked  difference. 

Testing  Machines. 

The  Fairbanks  cement  testing  machine  is  much  used  for  ce- 
ment testing  because  of  its  simplicity  and  automatic  action.  It 
is  shown  in  Fig.  144.  It  consists  of  a  cast  iron  frame  A,  made 
in  one  piece  with  a  shot  hopper  B.  To  this  frame  are  hung  the 
two  levers  D  and  C.  From  the  end  of  the  upper  lever  the  weight 
is  applied  by  allowing  shot  to  flow  from  the  hopper  into  the 
bucket  F.  The  tension  is  applied  to  the  briquettes  held  in  the 


440 


PORTLAND    CEMENT 


clips  N  and  N  by  means  of  the  lower  lever  C.  The  lower  clip 
it  attached,  by  means  of  a  ball  joint,  to  a  screw  with  a  hand 
wheel,  for  lowering  or  raising,  when  putting  in  the  briquette 
and  taking  up  the  slack.  There  is  also  a  counterbalance  E,  for 
bringing  the  levers  and  bucket  into  partial  equilibrium  so  that 
the  final  adjustment  can  be  made  with  the  ball  L.  The  shot 


Fig.  144. — Fairbank's  automatic  cement  testing  machine. 

hopper  is  provided  with  a  lever  and  gate  J,  which  cuts  off  the 
shot  as  soon  as  the  specimen  breaks.  The  shot  is  weighed  by 
hanging  the  bucket  on  the  opposite  end  of  the  lever  D,  by  means 
of  a  sliding  poise  R. 

To  operate  the  machine: 

Hang  the  cup  F  on  the  end  of  the  beam  D  as  shown  in  the 
illustration.  See  that  the  poise  R  is  at  the  zero  mark,  and  bal- 
ance the  beam  by  turning  the  ball  L. 

Fill  the  hopper  B  with  fine  shot,  place  the  specimen  in  the 
clamps  N  N,  and  adjust  the  hand  wheel  P  so  that  the  graduated 
beam  D  will  rise  to  the  stop  K.  Open  the  automatic  valve  J  so 
as  to  allow  the  shot  to  run  slowly  into  cup  F.  When  the  speci- 
men breaks,  the  graduated  beam  D  will  drop  and  automatically 
close  the  valve  J. 


TEN  811,3    STRENGTH  44! 

If  the  elasticity  of  the  cement  is  such  that  the  specimen  will 
not  break  before  the  beam  strikes  the  valve,  it  will  be  necessary 
to  stop  the  flow  of  shot  and  readjust  the  hand  wheel.  This  can 
best  be  done  by  lifting  the  end  of  the  beam  against  the  stop  by 
hand  and  tightening  the  hand  wheel  to  hold  the  beam  firmly  in 
position.  The  shot  is  then  allowed  to  run  until  the  specimen 
breaks. 

Remove  the  cup  with  the  shot  in  it,  and  hang  the  counterpoise 
weight  G  in  its  place. 

Hang  the  cup  F  on  the  hook  under  the  large  ball  E,  and  pro- 
ceed to  weigh  the  shot  in  the  regular  way,  using  the  poise  R  on 
the  graduated  beam  D,  and  the  weights  H  on  the  counterpoise 
weight  G. 

The  result  will  show  the  number  of  pounds  required  to  break 
the  specimen. 

The  flow  of  shot  can  be  regulated  by  the  cut-off  valve. 

In  breaking  a  specimen  in  the  above  form  of  the  Fairbanks 
machine,  it  is  necessary  to  screw  the  clips  up  tight  before  allow- 
ing the  shot  to  run  into  the  bucket,  in  order  to  guard  against 
having  to  do  this  later  on  in  the  breaking.  This  "initial  load" 
which  with  neat  briquettes  may  amount  to  at  least  400  Ibs.,  has 
been  given  as  one  of  the  chief  objections  to  this  machine.  The 
manufacturers,  however,  have  placed  on  the  market  a  new 
machine  in  which  the  hand  wheel  is  replaced  by  a  gear,  which  is 
actuated  by  a  worm,  which  in  turn  is  moved  by  a  crank  in  front 
of  the  machine.  This  does  away  with  the  initial  strain. 

Many  operators,  however,  prefer  the  older  form  as  it  is  auto- 
matic and  requires  no  attention  after  the  briquette  is  placed  in  the 
machine  and  the  shot  started  until  the  latter  has  to  be  weighed. 

The  Riehle  machine  (Fig.  145)  has  all  the  weight  upon  one 
long  graduated  beam.  The  load  is  applied  to  the  briquette  by 
means  of  the  lower  hand  wheel  which  actuates  a  worm  gear, 
while  the  beam  is  kept  in  balance  by  a  weight  which  is  moved 
along  the  beam  on  a  carriage  by  the  upper  hand  wheel.  The 
upper  lever  serves  as  an  indicator.  In  testing  a  briquette  both 
wheels  must  be  moved  simultaneously  so  that  the  indicator 
vibrates  in  the  center  of  the  gate.  In  testing  with  this  machine, 


442  PORTLAND    CEMENT 

the  briquette  is  placed  in  the  grips,  and,  being  carefully  adjusted, 
the  hand  wheel  connected  to  the  lower  grip,  is  turned  from  left 
to  right,  and  continued  until  the  indicator  of  weighing  beam 
(which  moves  in  a  gate  at  the  top  of  the  machine  and  nearly 
on  a  line  with  the  eye  of  the  operator)  drops.  This  indicator 
moves  the  reverse  of  the  weighing  beam,  and  when  too  much 
strain  is  exerted  it  falls,  and  when  too  much  weight  is  applied 


Fig.  145.— Riehle  cement  testing  machine. 

it  raises  to  the  top  of  the  gate.  It  is  important  that  the  indicator 
should  vibrate  in  the  center  of  the  gate,  and  rest  neither  up  nor 
down.  This  result  can  be  attained  by  carefully  manipulating  the 
large  hand  wheel  and  the  simultaneous  movement  of  the  poise 
on  the  weighing  beam.  When  the  indicating  beam  drops  down, 
when  the  test  first  begins,  the  rest  of  the  test  can  usually  con- 
tinue without  again  moving  the  large  hand  wheel,  which  is  shown 
underneath  the  end  of  the  shelf.  As  is  readily  understood,  the 


STRENGTH  443 

operator  propels  the  poises  backward  and  forward  by  means  of 
the  hand  wheel  (at  butt  end  of  weighing  beam)  and  cord  passing 
around  a  pulley  at  the  other  end  of  the  machine.  By  a  little 
practice  a  person  gets  very  expert,  and  can  make  a  test  with 
facility. 

Neither  of  these  machines  is  free  from  sources  of  error.  In  the 
Fairbanks  machine  there  is  an  error  due  to  the  fact  that  some  time 
(in  which  shot  is  falling  into  the  bucket)  is  taken  by  the  beam 
to  fall  to  the  valve  checking  the  shot  stream ;  even  then  there  is  a 
stream  of  shot  extending  from  the  valve  opening  to  the  surface 


Fig.  146.— Riehl£  U.  S.  standard  automatic  cement  tester. 

of  the  shot  in  the  bucket  which  must  fall  into  the  latter  and  be 
weighed  as  part  of  the  load  which  broke  the  specimen,  though 
this  slot  was  not  in  the  bucket  when  the  specimen  broke.  In 
the  Riehle  type  of  machine,  there  is  an  error  due  to  the  fact  that 
the  cord  is  attached  to  the  poise  at  a  point  not  on  a  line  with 
the  knife  edges  of  the  beam,  giving  the  poise  a  tendency  to  lift 
up  or  pull  down. 

Fig.  146  shows  the  Riehle  automatic  testing  machine. 

In  this  machine  the  initial  load  is  avoided  by  an  ingenious 
arrangement  consisting  in  balancing  a  bucket  of  shot  against 


444  PORTLAND 

a  weight,  and  then  applying  the  load  by  allowing  the  shot  to  run 
out  of  the  bucket. 

This  load  acting  through  the  levers  breaks  the  briquette. 
The  beam  should  be  kept  horizontal  by  means  of  the  lever  and 
worm  gear  so  that  the  pointer  and  mark  on  the  beam  are  at  all 
times  practically  coincident. 

At  the  instant  that  the  test  piece  breaks,  the  flow  of  shot  is 
shut  off  by  means  of  a  piston  valve.  The  slot  flowing  out  of  the 
kettle  is  caught  in  a  large  cup  resting  on  a  spring  balance,  which 
shows  at  all  times  the  load  which  has  been  applied  to  the 
briquette.  As  soon  therefore  as  this  latter  breaks,  the  operator 
can  see  at  a  glance  the  strain  required  to  do  this. 

These  machines  have  come  into  very  extensive  use  of  late 
years,  as  they  have  many  points  of  advantage  over  the  older 
forms.  For  instance  there  is  no  initial  load  applied.  The  break- 
ing stress  is  read  directly  as  soon  as  the  briquette  breaks  and 
there  is  no  transferring  of  the  shot  from  one  end  of  the  beam  to 
the  other  in  order  to  weigh  it.  The  weight  and  impact  of  the 
flowing  column  of  shot  is  also  done  away  with. 

The  Olsen  machine  is  shown  in  Fig.  147.  It  is  somewhat 
similar  to  the  Riehle  machine,  although  in  the  author's  opinion 
the  latter  possesses  some  points  of  advantage  over  the  former. 
In  this  machine  the  valve  is  different  from  that  of  the  Riehle  and 
an  initial  load  is  required  in  breaking  the  briquettes.  On  the 
other  hand  no  attention  is  required  from  the  operator  in  break- 
ing the  briquette  after  this  is  properly  centered  in  the  clips  and 
the  flow  of  shot  has  been  started.  The  Riehle  machine,  how- 
ever, can  be  used  in  this  way  if  thought  advisable. 

In  the  Olsen  machine  the  briquette  is  placed  in  the  clips  and 
the  load  applied  by  means  of  the  small  hand  v/heel  located  below 
these.  This  small  wheel  is  so  arranged  that  it  will  automatical- 
ly slip  on  the  adjusting  screw  as  soon  as  the  predetermined 
initial  load  has  been  applied  to  the  briquette.  The  cut-off  of 
shot  is  effected  by  the  upper  grip  striking  the  horizontal  arm 
which  extends  just  above  it,  and  thus  releasing  the  curved  arm 
carried  on  the  spindle  immediately  on  the  left.  This  curved 


TENSILE    STRENGTH  445 

arm  in  turn  strikes  the  valve  and  closes  it.     This  valve  mech- 


Fig  147. — Olsen  automatic  cement  testing  machine. 

anism  is  rather  complicated  and  is  liable  easily  to  get  out  of 
order. 

Rate  of  Stress. 

Whatever  machine  is  employed  to  break  the  briquettes  the 
load  is  to  be  applied  at  the  rate  of  600  Ibs.  per  minute.  The 
standard  load  for  many  years  was  400  Ibs.  per  minute  but  the 
committee  of  the  American  Society  of  Civil  Engineers  in  their 
report  of  1903  increased  this  to  the  above  figure.  The  more 
rapidly  the  load  is  applied  to  a  cement  briquette,  the  higher  the 


4/| 6  PORTLAND   CEMENT 

breaking  figure  which  will  be  obtained.  Any  of  the  automatic 
shot  testing  machines  described  above  can  be  set  so  that  the  load 
will  be  applied  at  a  uniform  rate.  With  the  lever  machines, 
however,  this'  can  only  be  attained  by  practice,  and  is  determined 
by  the  uniformity  with  which  the  poise  moves  over  the  beam. 
That  is,  in  one  minute  the  poise  should  travel  a  space  on  the 
beam  equivalent  to  600  pounds. 

Clips. 

Some  of  the  various  forms  of  clips  are  shown  in  the  following 
illustrations.     Fig.  148  shows  that  recommended  by  the  former 


Fig.  148. — Old  standard  clip. 

committee  of  the  American  Society  of  Civil  Engineers.  This 
form  does  not  seem  to  be  very  satisfactory  as  the  bearing  surface 
is  insufficient  and  the  briquette  is  likely  to  break  from  the  crush- 
ing of  its  surface  at  the  point  of  contact.  The  new  clip  Fig.  136 
on  page  431,  is  much  more  to  be  preferred.  It  affords  suffi- 
cient bearing  surface  without  binding. 

Various  authorities  at  different  times  have  advocated  cushion- 


Fig.  149.— Rubber  cushioned  clip. 

ing  the  grips  by  placing  blotting  paper  between  the  jaw  of  the 
grip  and  the  briquette,  or  stretching  rubber  bands  around  the 
jaws,  so  as  to  soften  the  point  of  contact  of  these  with  the  test 
piece.  Mr.  W.  R.  Cock1  has  advised  the  use  of  a  rubber  bear- 

1  Engineering  News,  Dec.  20,  1890. 


STRENGTH  447 

ing  as  shown  in  Fig,  149.  In  this  clip  the  line  of  contact  be- 
tween the  grip  and  the  briquette  is  a  rubber  tube  mounted  on  a 
pin.  These  tubes  are  readily  replaced  for  a  few  cents  when 
worn  out.  These  cushion  clips  usually  give  results  which  are 
only  80  to  90  per  cent,  of  those  obtained  with  the  standard  clips. 
The  cushion  clips  "are  also  troublesome. 

Rocker  and  roller  clips  (Fig.  150)  are  also  upon  the  market 
and  the  latter  are  much  used.  Roller  bearings  are  likely  to  wear 
flat  unless  they  are  kept  clean  and  can  revolve  freely.  This  it  is 
hard  to  do.  Roller  clips  do  not  give  breaks  that  are  any  higher 
than  those  obtained  with  the  Standard  rigid  form.  The  general 
impression  seems  to  be  that  clip  breaks  are  due  to  cross  strains 
and  hence  give  figures  below  the  true  breaking  strength  of  the 


Fig.  150.— Roller  clips. 

cement.  In  fact,  experiments  prove  that  clip  breaks  are  on  an 
average  from  2  to  5  per  cent,  higher  than  breaks  obtained  at  the 
cross  section. 

In  order  that  the  stress  upon  the  briquette  shall  be  along 
the  proper  lines  great  care  must  be  exercised  in  properly  center- 
ing the  briquette  in  the  clips,  and  the  form  of  the  latter  must  be 
such  that  it  does  not  clamp  the  head  of  the  briquette  thus  pre- 
venting the  test  piece  from  adjusting  itself  to  an  even  bearing. 
At  the  same  time  the  surface  of  contact  must  be  sufficient  to 
prevent  the  briquette  from  being  crushed  at  this  point.  Striking 
the  happy  medium  has  so  far  proved  not  any  too  easy.  The 
clips  are  usually  suspended  by  conical  bearings  which  permit 


4/|  8  PORTLAND 

them  to  turn  so  as  always  to  transmit  the  stress  in  a  direct  line 
between  the  bearings. 

Lack  of  Uniformity  in  Tensile  Tests. 

In  cement  testing,  the  personal  equation  enters  very  largely 
into  the  results.  In  a  paper1  by  Prof.  James  Madison  Porter,  of 
Lafayette  College,  he  gave  a  series  of  results  upon  the  same  ce- 
ment by  nine  different  operators,  tested  by  the  method  of  the  So- 
ciety of  Civil  Engineers  as  they  understood  it.  The  results  varied 
from  75  to  247  pounds  per  square  inch.  The  first  Committee  on 
a  Uniform  System  for  Tests  of  Cement  of  the  American  Society 
of  Civil  Engineers,  in  their  report,  says: 

"The  testing  of  cement  is  not  so  simple  a  process  as  it  is  thought  to  be. 
No  small  degree  of  experience  is  necessary  before  one  can  manipulate  the 
materials  so  as  to  obtain  even  approximately  accurate  results. 

"The  first  test  of  inexperienced,  though  intelligent  and  careful  persons, 
are  usually  very  contradictory  and  inaccurate,  and  no  amount  of  experience 
can  eliminate  the  variations  introduced  by  the  personal  equations  of  the 
most  conscientious  observers.  Many  things,  apparently  of  minor  import- 
ance, exert  such  a  marked  influence  upon  the  results,  that  it  is  only  by  the 
greatest  care  in  every  particular,  aided  by  experience  and  intelligence  that 
trustworthy  tests  can  be  made." 

The  personal  equation  probably  plays  its  most  important  part 
in  the  gauging  of  the  cement,  the  making  of  the  mortar,  and  the 
molding  and  breaking  of  the  briquettes.  In  order  to  eradicate 
these  variations  of  treatment,  machines  have  been  introduced 
upon  the  market  to  do  the  work  automatically  and  so  do  away 
with  whatever  variations  the  operator  may  introduce  into  the 
hand  work,  principally  among  which  are  the  Steinbrilch  and  the 
Faija  mixers  and  the  Bohme  hammer. 

Machines  for  Mixing  the  Mortar. 

The  Steinbrilch  mixer,  (Fig.  151),  is  much  used  in  Germany 
and  gives  good  results;  the  chief  objection  to  its  universal  adop- 
tion in  this  country  is  its  cost,  about  $130.  It  consists  of  a  circu- 
lar shell  having  on  its  upper  side,  near  the  outer  edge  a  groove  or 
trough  in  which  the  mortar  is  mixed.  A  wheel,  whose  rim  corre- 

1  Engineering  News,  March  7,  1895. 


STRENGTH 


449 


spends  with  the  groove  in  the  pan,  rests  in  this  trough  and  re- 
volves around  a  fixed  horizontal  axis,  which  is  above  and  nor- 
mal to  the  axis  of  the  pan.  The  pan  is  now  made  to  revolve 
about  its  vertical  axis,  and  at  the  same  time  the  wheel  is  made  to 
revolve  about  its  horizontal  axis,  along  with  the  pan  and  at  the 


Fig.  151. — Steinbriich  mixer. 

same  rate  of  speed,  by  means  of  gearing.  The  mortar  is  thus 
rubbed  between  the  outer  rim1  of  the  wheel  and  the  inner  surface 
of  the  trough.  Small  plows  scrape  the  mortar  from  the  sides  of 
the  trough,  as  the  latter  revolves,  thus  keeping  the  mortar  in  the 
bottom  of  the  trough  and  under  the  wheel.  When  the  mixing  is 
complete,  which  according  to  the  German  rules  requires  two  and 
one-half  minutes,  the  wheel  and  plows,  the  axis  of  which  are 
hinged,  are  lifted  from  the  trough  and  the  mortar  taken  out.  The 
apparatus  appears  unnecessarily  complicated,  and  it  seems  as  if 
a  simpler  and  less  expensive  form  might  be  devised  and  used  to 
advantage. 

The  Faija  mixer  is  the  design  of  the  late  Henry  Faija,  of  Eng- 
land. Fig.  152  shows  the  mixer  as  made  by  Riehle  Bros.  Testing 
Machine  Co.,  of  Philadelphia.     It  consists  of  a  circular  pan  of 
29 


450  PORTLAND    CEMENT 

about  one  foot  in  diameter,  within  which  revolve  the  arms  of  a 
stirrer.  These  arms  revolve  around  their  own  axis  in  one  direc- 
tion and  around  the  pan  in  the  reverse  direction.  This  motion  is 
given  them  by  a  fixed  internally  toothed  wheel  which  actuates  the 
pinion  of  the  stirring  spindle.  To  operate,  first  find  by  means  of 
a  trial  test  by  hand  gauging  the  proper  proportion  of  water  to  ce- 
ment. Next  place  in  the  mixer  sufficient  cement  to  fill  a  gang 


Fig.  152. — Faija  mixer. 

of  molds  and  add  at  once  the  proper  quantity  of  water  for  this 
weight  of  cement.  Then  turn  the  handle  of  the  machine  fairly 
quickly  for  from  a  half  to  three-quarters  of  a  minute,  when  it 
will  be  found  that  the  cement  and  water  are  thoroughly  mixed 
and  ready  for  the  molds.  In  gauging  cement  and  sand  in  this 
machine,  first  mix  the  cement  and  sand  dry  and  then  add  the 
water,  etc. 

Machines  for  Molding  the  Briquettes, 

The  Bohme  hammer  consists  of  a  tilt  hammer  with  automatic 
action.  The  hammer  is  thus  described  by  Max  Gary  i1  "The 
hammer  is  driven  by  a  cam  wheel  of  ten  cams  actuated  by  simple 
gearing.  The  wrought  iron  handle  of  the  hammer  is  let  into  the 
cross-head  which  carries  the  axle  of  the  hammer  and  keyed  to 
this  cross-head  and  to  the  cap  so  that  it  may  be  replaced  if  worn. 
The  steel  hammer  weighing  4^  pounds,  is  similarly  fastened  to 
the  cap.  As  soon  as  the.  intended  number  of  blows  has  been  de- 

1  Trans.  Am.  Soc.  C.  E.,-3°,  i. 


TENSILE    STRENGTH 


451 


livered,  the  mechanism  is  automatically  checked,  the  proper  set- 
ting having  been  made  for  this  purpose  before   beginning  the 


Fig.  153. — Bohme  hammer. 

work."     (The  number  of  blows  required  in  the  German  Standard 
test  is   150). 

OBSERVATIONS. 

High  Tensile  Strength  of  Unsound  Cements. 

Perhaps  the  results  of  no  test  are  given  so  prominent  a  place 
in  the  manufacturers'  advertisement  as  the  neat  strength  of  bri- 
quettes made  of  his  brand.  We  hear  the  question  constantly  pro- 
pounded by  the  prospective  purchaser  of  "How  much  does  your 
cement  pull?"  and  a  thousand-pound  neat  7  day  break  is  consid- 
ered compensation  for  all  the  deleterious  qualities  a  cement  may 
have.  In  reality,  the  neat  break  is  not  of  so  much  value  as  we 


452 


PORTLAND    CKMKNT 


are  apt  to  suppose,  and  taken  by  itself  is  little  criterion  of  the 
quality  of  cement.  Unsound  cements  often  give  notoriously 
high  results,  and  the  addition  of  plaster  or  gypsum  will  also  in- 
crease the  neat  strength.  In  both  of  these  instances  there  is 
apt  to  be  on  long  time  breaks  a  falling  off  in  strength,  permanent 
in  the  former  case  and  usually  only  temporary  in  the  latter  case. 
This  is  illustrated  by  the  following  table  taken  from  a  paper  by 
Mr.  W.  P.  Taylor,  on  "Soundness  Tests  of  Portland  Cement,"1 
read  in  1903.  This  table  was  compiled  from  over  200  nearly  con- 
secutive tests  of  a  single  brand,  100  of  them  failing  in  the  test 
100  passing. 

TABLE  XLII.— COMPARISON  OF  THE  TENSILE  STRENGTH  OF  BRI- 
QUETTES PASSING  AND  FAILING  IN  THE  BOILING  TEST. 


Age 

F'ailing 

Passing 

Neat 

1  :^ 

sand 

Neat 

sand 

530 
817 
749 
7i3 
702 

197 
2/3 
2/4 

242 

391 
643 
727 
732 
749 

237 
303 
3I2 

3H 

28  days 

It  will  be  noticed  that  the  early  strength  of  the  neat  tests  of 
those  samples  failing  to  pass  the  test  is  much  the  greater,  while 
the  opposite  is  true  of  the  sand  samples. 

Rotation  Between  Neat  and  Sand  Strength. 

That  the  sand  strength  and  neat  tests  do  not  necessarily  bear 
any  relation  to  each  other,  the  Table  XLII  I  will  show.  The 
sand  strength  seems  to  depend  largely  upon  the  fineness,  yet  dif- 
ferent brands  of  cement  giving  similar  residues  on  the  test  sieves 
will  not  necessarily  show  the  same  relation  between  neat  and  sand 
test.  This  latter  may,  of  course,  be  due  to  differences  in  the 
amount  of  flour,  which  is  not  shown  by  the  sieve  test,  as  well  as 
to  peculiarities  of  composition,  physical  structure,  etc.,  of  the 
clinker  from  which  the  cement  is  ground. 

1  Proceedmgs  Amer.  Soc.  Test.  Mat.,  III.  (1903),  381. 


TENSILE  STRENGTH 


453 


Drop  in  Tensile  Strength. 

Another  point  which  has  often  been  brought  against  cement, 
and  American  cements  in  particular,  is  that  there  is  a  permanent 
drop  in  tensile  strength  after  28  day  test.  In  fairly  quick-setting 
cements  with  their  usual  low-lime  content  and  to  which  the  nor- 
mal amount  of  gypsum  or  plaster  has  been  added,  this  drop  is 
rarely  met  with  and  is  probably  then  due  to  improper  manipula- 
tion of  the  test.  In  cements  high  in  lime,  without  being  nec- 
essarily unsound,  or  in  cements  to  which  a  large  addition  of 
plaster  or  gypsum  has  been  made,  this  drop  is  often  met  with. 
In  unsound  cements  it  is  usually  met  with,  often  after  the  7  day 
test. 

It  does  not  necessarily  follow  that  any  drop  in  strength  indi- 
cates a  disrupting  action,  because  as  cement  briquettes  get  older 
they  get  more  and  more  brittle,  and  consequently  tensile  stresses 
break  them  more  easily.  Particularly  is  this  true  if  the  clips 
exert  any  twisting  action  and  the  load  is  not  evenly  applied. 
Also  cement  is  never  used  neat  and  in  the  vast  majority  of  cases 

TABLE  XLTII.— SHOWING  LACK  OF  ANY  RELATION  BETWEEN  NEAT 
AND  SAND  STRENGTH. 


Cement 
No. 

Boiling 
test 

Fineness 

Tensile  strength 
7  days 

Tensile  strength 
28  days 

Through 
No.  100 

Through 
No.  200 

Neat 

i  :3 

Neat 

i  :  3 

I 

0.  K. 

99.0 

8o.O 

915 

303 

1013 

353 

2 

0.  K. 

99.0 

8o.O 

790 

285 

853 

320 

3 

O.  K. 

99.1 

85.I 

933 

990 

340 

4 

O.  K. 

98.8 

83.3 

930 

2§8 

9^3 

330 

0.  K. 

94.8 

78.8 

733 

270 

825 

360 

6 

0.  K. 

95-0 

79.0 

748 

280 

620 

275 

7 

O.  K. 

96.5 

74.0 

818 

273 

858 

360 

8 

O.  K. 

97.0 

74.0 

800 

260 

1013 

280 

9 

O.  K. 

95-1 

7O.O 

910 

190 

1038 

266 

10 

O.  K. 

70.0 

683 

180 

750 

320 

ii 

0.  K. 

98.0 

82.5 

1008 

200 

i«5 

2-S2 

12 

0.  K. 

97-9 

82.5 

855 

283 

970 

333 

13 

O.  K. 

94.8 

75-0 

610 

350 

810 

440 

H 

O.  K. 

92.0 

70.0 

544 

206 

884 

261 

15 

O.  K. 

93-4 

70.4 

701 

217 

893 

310 

16 

O.  K. 

93-8 

74.2 

680 

359 

791 

410 

17 

0.  K. 

97.1 

82.5 

855 

283 

970 

333 

18 

0.  K. 

97-4 

82.7 

910 

255 

970 

305 

454 


PORTLAND    CEMENT 


when  a  cement  shows  a  slight  falling  off  in  neat  strength,  the 
sand  strength  increases  with  age.  This  is  shown  in  Table  XLJV 
Humphreys  states  that  the  compressive  strength  of  neat  cement 
does  not  experience  this  drop  when  the  cement  is  sound  even 
if  the  tensile  strength  does  fall  off  somewhat  after  the  28  day 
test;  an  important  fact,  if  true,  as  cement  is  seldom  if  ever  used 
in  tension. 

Coarse  grinding  of  the  cement  has  some  influence  on  the  in- 
crease in  strength  with  age.  A  very  fine  cement  increases  neat 
very  little  after  7  days,  while  a  coarser  one  keeps  on  increasing. 
This  is  no  doubt  due  to  the  fact  that  the  coarse  particles  are  acted 
on  much  slower  than  the  fine  ones,  and  solution  and  crystalliza- 
tion of  these  go  on  after  the  finer  ones  are  all  hydrated.  The  fol- 

TABLE  XLIV. — SHOWING  Loss  IN  STRENGTH  OF  NEAT  BRIQUETTES  AND 
GAIN  IN  SAND  BRIQUETTES  AFTER  SEVEN  DAY  TEST. 


0 

Tensile  strength 

e 

S 

Boiling 
test 

Neat 

i  :  3  sand 

8 

7  days 

28  days 

3  mos. 

6  rnos. 

ryr. 

7  days 

28  days 

3 
mos. 

6 
mos. 

i  year 

i 

O.  K. 

657 

615 

650 

680 

711 

240 

302 

360 

381 

405 

2 

O.  K. 

915 

845 

73° 

76o 

755 

310 

375 

378 

415 

3 

0.  K. 

1058 

1023 

890 

852 

783 

200 

263 

425 

410 

463 

4 

O.  K. 

865 

727 

730 

650 

728 

317 

353 

390 

400 

416 

5 

O.  K. 

708 

656 

661 

663 

665 

2OI 

279 

402 

455 

520 

6 

O.  K. 

735 

704 

684 

688 

658 

290 

401 

426 

443 

477 

7 

O.K. 

916 

845 

816 

825 

802 

301 

360 

424 

450 

456 

8 

0.  K. 

IOI2 

875 

890 

921 

944 

306 

374 

410 

467 

9 

0.  K. 

9I2 

815 

826 

814 

827 

292 

327 

368 

381 

381 

10 

0.  K. 

856 

803 

810 

814 

811 

275 

369 

391 

418 

ii 

check'd 

1150 

775 

610 

615 

674 

235 

315 

366 

38i 

427 

12 

' 

947 

816 

702 

310 

Dis. 

210 

246 

247 

3" 

312 

13 

' 

812 

304 

318 

301 

204 

294 

316 

321 

330 

327 

14 

' 

955 

811 

816 

802 

503 

274 

321 

375 

416 

427 

15 

' 

927 

802 

765 

612 

344 

213 

227 

264 

375 

414 

16 

' 

610 

314 

191 

78 

95 

224 

237 

241 

256 

281 

17 

1110 

765 

342 

Dis. 

Dis. 

275 

298 

315 

362 

396 

lowing  experiment  was  made  with  the  same  cement.  Cement  A 
is  just  as  it  comes  from  the  mills.  Cement  B  is  cement  A  with 
the  coarse  particles  (residue  on  a  No.  200  sieve,  removed)  : 


TENSILE    STRENGTH 


455 


Age 

7  days 

28  days 

3  mos. 

6  mos. 

9  mos. 

Cement  A  Ibs  •  • 

618 

60  «: 

A~- 

Cement  B  Ibs  •  •                     .... 

CT« 

°y5 

c.,6 

°/O 

/•*O 

75° 

CAn 

D10 

D4U 

JOO 

JLU 

o49 

Of  76  samples  of  the  same  brand  of  cement,  each  one  contain- 
ing from  63.25  to  63.75  Per  cent-  n'me  when  freshly  ground  and 
passing  the  boiling  test,  those  ground  to  a  fineness  of  80-85  Per 
cent,  through  a  No.  200  sieve  showed  an  increase  of  only  3.4  per 
cent,  neat  strength  between  the  periods  of  7  and  28  days;  while 
those  ground  to  a  fineness  of  70-75  per  cent,  through  a  No.  200 
sieve  gained  18.3  per  cent,  in  this  time.  When  a  cement  gives  a 
high  neat  break  on  7  days,  and  passes  the  steam  test  when  re- 
ceived, failure  to  show  a  marked  increase  in  28  days  should  not 
be  taken  as  an  indication  of  a  poor  cement  nor  should  the  cement 
be  rejected  because  of  this.  Indeed,  if  the  sand  test  shows  an  in- 
crease in  strength  in  the  28  day  break,  the  cement  should  be 
promptly  accepted. 


Chapter   XVIII. 


SOUNDNESS. 

STANDARD  SPECIFICATION  AND  METHOD  OF  TEST. 

Specification. — Pats  of  neat  cement  about  three  inches  in  diam- 
eter, one-half  inch  thick  at  the  center,  and  tapering  to  a  thin 
edge,  shall  be  kept  in  moist  air  for  a  period  of  twenty-four  hours. 

(a)  A  pat  is  then  kept  in  air  at  normal  temperature  and  ob- 
served at  intervals  for  at  least  28  days. 

(b)  Another  pat  is  kept  in  water  maintained  as  near  70°  F.  as 
practicable,  and  observed  at  intervals  for  at  least  28  days. 

(c)  A  third  pat  is  exposed  in  any  convenient  way  in  an  atmos- 
phere of  steam,  above  boiling  water,  in  a  loosely  closed  vessel  for 
five  hours. 

These  pats,  to  satisfactorily  pass  the  requirements,  shall  re- 
main firm  and  hard  and  show  no  signs  of  distortion,  checking, 
cracking  or  disintegrating. 

Significance. — The  object  is  to  develop  those  qualities  which 
tend  to  destroy  the  strength  and  durability  of  a  cement.  As  it 
is  highly  essential  to  determine  such  qualities  at  once,  tests  of 
this  character  are  for  the  most  part  made  in  a  very  short  time, 
and  are  known,  therefore,  as  accelerated  tests.  Failure  is  re- 
vealed by  cracking,  checking,  swelling,  or  disintegration,  or  all 
of  these  phenomena.  A  cement  which  remains  perfectly  sound 
is  said  to  be  of  constant  volume. 

Methods. — Tests  for  constancy  of  volume  are  divided  into 
two  classes:  (i)  normal  tests,  or  those  made  in  either  air  or 
water  maintained  at  about  21°  Cent.  (70°  Fahr.),  and  (2)  accele- 
rated tests,  or  those  made  in  air,  steam,  or  water  at  a  temperature 
of  45°  Cent.  (113°  Fahr.)  and  upward.  The  test  pieces  should 
be  allowed  to  remain  24  hours  in  moist  air  before  immersion  in 
water  or  steam,  or  preservation  in  air. 

For  these  tests,  pats,  about  7^2   cm.    (2.95   in.)    in  diameter, 


SOUNDNESS 


457 


\y\.  cm.  (0.49  in.)  thick  at  the  center,  and  tapering  to  a  thin 
edge,  should  be  made,  upon  a  clean  glass  plate  [about  10  cm. 
(3.94  in.)  square],  from  cement  paste  of  normal  consistency. 

Normal  Test. — A  pat  is  immersed  in  water  maintained  as  near 
21°  Cent.  (70°  Fahr.)  as  possible  for  28  days,  and  observed  at 
intervals.  A  similar  pat,  after  24  hours  in  moist  air,  is  main- 
tained in  air  at  ordinary  temperature  and  observed  at  intervals. 


Fig.  154. — Apparatus  for  making  boiling  tests. 

Accelerated  Test. — A  pat  is  exposed  in  any  convenient  way 
in  an  atmosphere  of  steam,  above  boiling  water,  in  a  loosely 
closed  vessel,  for  5  hours.  The  apparatus  recommended  for 
making  these  determinations  is  shown  in  Fig.  154. 

To  pass  these  tests  satisfactorily,  the  pats  should  remain  firm 
and  hard,  and  show  no  signs  of  cracking,  distortion  or  disinte- 
gration. 

Should  the  pat  leave  the  plate,  distortion  may  be  detected  best 


458 


PORTLAND    CEMENT 


with  a  straight  edge  applied  to  the  surface  which  was  in  contact 
with  the  plate. 

In  the  present  state  of  our  knowledge  it  cannot  be  said  that 
cement  should  necessarily  be  condemned  simply  for  failure  to 
pass  the  accelerated  tests ;  nor  can  a  cement  be  considered  entire- 
ly satisfactory  simply  because  it  has  passed  these  tests. 

NOTES. 

The  form  of  pat  boiler  shown  in  Fig.  154  is  somewhat  larger 
and  more  complicated  than  is  usually  considered  necessary  for 
this  purpose.  The  writer  has  employed  a  smaller  boiler  con- 
taining a  rack  upon  which  rest  several  shelves,  one  above  the 
other.  The  arrangement  is  shown  in  Fig.  155.  The  entire  rack 


Fig-  155.— Simple  pat  boiler  and  steamer. 

is  removable  from  the  boiler  and  the  shelves  are  slipped  out  side- 
wise.  The  pats  to  be  steamed  are  placed  on  the  upper  shelves 
of  the  rack  and  those  to  be  boiled  upon  the  lower.  Sufficient 
water  is  added,  which  amount  can  easily  be  determined  by 
experiment,  to  allow  five  hours  boiling  without  the  pats  on  the 
second  shelf  from  the  bottom  becoming  uncovered,  or  a  constant 
level  bottle  may  be  attached.  This  consists  merely  of  a  bottle 
with  an  opening  at  the  bottom  as  shown  in  Fig.  156.  Through 
the  rubber  stopper  of  this  bottle,  a  glass  tube  is  passed,  with  the 
lower  end,  b,  of  this  on  a  level  with  the  point  in  the  pat  boiler  at 
which  it  is  desired  to  maintain  the  surface  of  the  water.  When- 


SOUNDNESS 


459 


ever  the  water  in  the  boiler  reaches  a  point  below  that  of  the 
bottom  of  the  tube,  water  will  flow  in  from  the  bottle. 

The  pat  boiler  should  always  have  a  hole  in  the  cover  through 
which  the  steam  may  escape.  In  some  laboratories  steam  is 
used  to  heat  the  pat  boiler  and  in  such  instances,  as  indeed  when 
the  boiler  is  heated  by  a  flame,  the  opening  should  be  large 
enough  not  to  permit  any  pressure  in  the  boiler. 

When  only  a  few  tests  have  to  be  made  a  convenient  form 
of  boiler  consists  of  a  common  tin  bucket  provided  with  a  tin  top. 
A  small  hole  to  permit  exit  of  the  steam  is  made  in  the  top  and  a 


Fig.  156. — Constant  water  level  apparatus. 

shelf  of  wire  net  or  perforated  tin  is  placed  in  the  bucket  and 
supported  by  any  appropriate  means  at  least  two  inches  above 
the  water  level.  The  pats  are  set  on  this  shelf.  A  still  better 
pat  test  apparatus  consists  of  a  galvanized  iron  bucket  on  the 
bottom  of  which  rests  a  perforated  pie  plate.  The  pats  to  be 
boiled  are  placed  on  this  and  it  is  also  provided  with  a  rack  of 
Y$  inch  mesh  galvanized  wire  netting.  This  rack  stiffened  with 
a  wire  ring  soldered  to  it  and  bent  up  at  two  places  to  form  a 
handle.  Such  a  pat  boiler  will  last  a  long  time,  stand  rough  ser- 
vice and  permit  of  the  steaming  and  boiling  of  four  or  five  pats 
of  cement  at  one  time. 


460  PORTLAND   CEMENT 

A  great  many  cement  testers  steam  the  pat  for  five  hours  and 
then  boil  them  a  few  hours,  the  idea  being  that  the  boiling  will 
bring  out  any  injurious  qualities  not  shown  by  the  steam  test. 
The  boiling  test  is  generally  considered  the  more  severe  test 
although  the  writer's  experience  has  been  that  the  difference  be- 
tween the  two  tests  has  not  been  nearly  so  marked  as  is  generally 
supposed. 

The  boiling  test  should  always  be  made  with  fresh  water  and 
any  accumulation  of  lime  and  other  sediments  in  the  bottom  of 
the  pat  boiler  should  be  carefully  scraped  out  each  time  before 
filling.  Pats  should  also  be  supported  from  the  bottom  of  the 
boiler  so  that  they  do  not  come  in  contact  with  the  latter.  As 


Fig.  157.— Shrinkage  and  disintegration  cracks. 

it  is  easy  to  see,  a  pat  formed  on  glass  will  have  a  very  smooth 
under  side  and  will  come  into  sufficient  close  contact  with  the 
bottom  of  the  pat  boiler  to  receive  the  heat  directly  through  the 
latter  and  thus  have  its  under  side  heated  to  a  very  much  higher 
temperature  than  that  of  the  boiling  water  surrounding  it. 

Cracks  due  to  disintegration  should  not  be  confused  with  those 
caused  by  drying  of  the  pat.  The  former  are  wedge  shaped  and 
radiate  from  the  center  of  the  pat,  while  the  latter  usually  run 
across  the  middle  of  the  pat  or  around  its  edges.  Fig.  157 
illustrates  the  two  forms  of  cracks.  A  is  a  shrinkage  crack  and 
B  cracking  caused  by  expansion.  Shrinkage  cracks,  due  to  dry- 
ing, are  usually  developed  in  a  day  or  two  and  are  due  to  too  thin 
(wet)  a  paste,  to  allowing  the  pat  to  harden  in  the  air  instead 
of  the  moist  closet  or  to  lack  of  humidity  in  the  moist  closet. 


SOUNDNESS  461 

Disintegration,  cracks  rarely  appear  in  either  air  or  cold  water 
pats  until  after  two  or  three  days  and  are  due  to  unsoundness. 

The  failure  of  the  pats  to  remain  on  the  glass  does  not 
necessarily  indicate  that  the  cement  from  which  they  are  made  is 
unsound.  Likewise  the  cracking  of  the  glass  to  which  the  pat 
is  attached  during  boiling  means  nothing  to  condemn  the  cement 
and  is  due  merely  to  unequal  expansion  of  the  pat  and  glass  and 
the  firm  adhesion  of  the  one  to  the  other. 

Pats  which  are  boiled  or  steamed  usually  disintegrate  in  a  very 
marked  manner  where  the  cement  is  at  all  unsound.  Usually 
disintegration  is  so  marked  that  the  pat  may  be  easily  crumbled 
between  the  fingers.  The  first  indications  of  failure  are  usually 
the  appearance  of  radial  cracks,  although  not  always,  and  this  is 
/  followed  by  more  or  less  checking  over  the  entire  surface  of  the 
pat.  Pats  which  are  sound  will  usually  be  found  to  break  be- 
tween the  thumb  and  finger  sharply,  with  a  marked  snap,  while 
those  which  are  unsound  will  more  or  less  crumble.  Pats  made 
of  sound  cement  are  always  hardened  by  boiling.  Those  made 
of  unsound  cement  are  weakened. 

Pats  should  always  be  allowed  24  hours  to  harden  before 
boiling.  Sometimes  pats  will  stand  the  boiling  or  steam  test 
when  this  is  applied  before  the  pat  hardens  although  they  would 
not  do  this  if  allowed  to  remain  24  hours  before  boiling.  Again 
the  reverse  of  this  is  true. 

OTHER  METHODS. 
German  Specifications. 

The  standard  German  specifications  until  recently  included  an 
accelerated  test  something  like  our  own  steam  test.  This  has 
been  abandoned,  however,  and  the  new  rules  recognize  only  the 
cold  water  test  and  prescribe  that  this  shall  be  carried  out  in  the 
following  manner. 

Portland  cement  must  be  volume  constant.  It  shall  be  recog- 
nized as  decisive  proof  of  this  when  a  pat  of  neat  cement,  pre- 
pared on  a  glass  plate,  protected  from  drying  out,  and  placed 


462  PORTLAND    C£M£NT 

under  water  after  24  hours,  shows  no  sign  of  curvature  or  crack- 
ing on  the  edge,  even  after  a  long  time. 

For  this  test  the  pat  made  for  judging  the  setting  process  is, 
with  slow-setting  cement,  put  under  water  after  24  hours,  but  in 
any  case  only  after  being  hard  set.  With  quick-setting  cement 
this  can  be  done  after  a  shorter  time.  The  pats,  especially  those 
of  slow-setting  cements,  should  be  protected  from  drying  out  by 
storing  in  a  covered  box  until  the  setting  is  finished.  If  the  pats, 
while  under  water,  curve  or  show  cracks  on  the  edge,  this  indi- 
cates undoubted  expansion  of  the  cement,  i.e.,  in  consequence  of 
the  increase  of  volume  disintegration  of  the  cement  occurs  by 
gradual  loss  of  coherence,  leading  to  complete  crumbling. 

The  signs  of  change  in  volume  are  generally  shown  after  three 
days ;  in  any  case  an  observation  of  28  days  is  sufficient. 

Faija's  Test. 

Probably  the  mildest  of  the  hot  tests  is  that  of  the  English  ce- 
ment expert,  Henry  Faija.  His  method  consists  in  subjecting  a 
freshly  gauged  pat  upon  a  plate  of  glass  prepared  as  directed 
above  to  a  moist  heat  of  100°  to  105°  F.  for  six  or  seven  hours, 
or  until  thoroughly  set,  and  then  immersing  it  in  water  kept  at  a 
temperature  of  115°  to  120°  F.  for  the  remainder  of  the  twenty- 
four  hours.  This  treatment  imparts  an  artificial  age  to  the  cement 
and  quickly  brings  out  any  vicious  qualities  the  cement  may  pos- 
sess. For  this  test  he  used  the  apparatus  shown  in  Fig.  158.  It 
consists  of  a  covered  vessel  in  which  water  is  kept  at  the  even 
temperature  of  115°  to  120°  F.  by  means  of  a  water-jacket.  The 
inner  vessel  is  filled  with  water  to  the  height  shown.  Above  the 
water  level  is  placed  a  rack.  When  the  water  in  the  inner  vessel 
is  at  the  temperature  of  from  115°  to  120°  F.,  the  upper  part  of 
the  vessel  will  be  filled  with  aqueous  vapor  and  this  latter  will  be 
at  a  temperature  of  from  100°  to  105°  F.  As  soon  as  the  pat  is 
gauged  it  is  put  on  the  rack  and  left  there  for  six  hours.  It  is 
then  placed  in  the  warm  water  and  allowed  to  remain  eighteen 
hours  longer.  The  author  of  the  test  states  that  if  a  test  pat 
after  the  above  treatment  shows  no  signs  of  cracking  or  blowing 


SOUNDNESS 


463 


and  adheres  firmly  to  the  glass  plate  on  which  it  was  made,  it 
may  be  used  with  perfect  confidence;  it  will  never  blow.  This 
test  certainly  seems  fairer  to  the  cement  than  most  of  the  hot 


Fig.  158.— Faija's  soundness  test  apparatus. 

tests,  many  of  which  would,  if  applied  to  some  good  cements, 
cause  them  to  be  rejected. 

Kiln  Test. 

Dr.  Bohme  suggested  the  kiln  test.  This  test  was  until  recent- 
ly considered  as  the  standard  German  accelerated  test  for  sound- 
ness. It  has  now  however  been  abandoned  and  the  cold  water 
pat  test  substituted.  The  test  was  carried  out  as  follows: 

A  stiff  paste  of  neat  cement  and  water  is  made,  and  from  this 
cakes  8  cm.  to  10  cm.  in  diameter  and  I  cm.  thick  are  formed  on 
a  smooth  impermeable  plate  covered  with  blotting  paper.  Two 
of  these  cakes  which  are  to  be  protected  against  drying  in  order 
to  prevent  drying  cracks,  are  placed  after  the  lapse  of  twenty- 


464  PORTLAND    CEMENT 

four  hours,  or  at  least  only  after  they  have  set,  with  their  smooth 
surface  on  a  metal  plate  and  exposed  for  at  least  one  hour  to  a 
temperature  of  from  110°  C.  to  120°  C.  until  no  more  water 
escapes.  For  this  purpose  the  drying  closets  in  use  in  chemical 
laboratories1  may  be  utilized.  If  after  this  treatment  the  cakes 
show  no  edge  cracks,  the  cement  is  to  be  considered  in  general 
of  constant  volume.  If  such  cracks  do  appear  the  cement  is 
not  to  be  condemned,  but  the  results  of  the  decisive  test  with  the 
cakes  hardening  on  glass  plates  under  water  must  be  waited  for. 
It  must,  however,  be  noticed  that  the  heat  test  does  not  admit 
of  a  final  conclusion  of  the  constancy  of  volume  of  those  cements 
which  contain  more  than  3  per  cent,  of  calcium  sulphate  (gyp- 
sum) or  other  sulphur  combinations. 

Prof.  Tetmajer,  of  Zurich,  modifies  this  method  by  placing  on 
the  bottom  of  the  oven  a  few  millimeters  of  water.  The  heat  is 
gradually  applied  so  as  to  evaporate  all  the  water  in  from  three 
to  six  hours;  first  that  on  the  floor  of  the  oven,  and  then  that 
absorbed  by  the  mortar.  The  latter  is  held  on  a  shelf  above  the 
floor.  The  temperature  of  the  oven  remains  at  about  95°  C.  until 
the  water  is  entirely  evaporated.  After  this  the  heating  is  contin- 
ued half  an  hour  longer  in  such  a  manner  as  to  raise  the  tempera- 
ture of  the  oven  to  120°  C.  This  will  bring  the  temperature  of 
the  interior  of  the  briquette  at  a  little  over  100°  C.  It  is  difficult 
to  obtain  comparative  results  by  this  method  as  the  heat  is  not 
the  same  for  all  specimens,  since  after  the  evaporation  of  the 
water,  the  heat  is  much  greater  at  the  bottom  than  at  the  top  of 
the  oven. 

Boiling  Test. 

This  test,  devised  by  Dr.  Michaelis,  is  very  similar  to  the 
one  just  given.  It  consists  in  rolling  a  ball  of  mortar  and  then 
flattening  the  ball  to  the  thickness  of  half  an  inch.  The  consist- 
ency of  the  mortar  should  be  such  that  is  shall  neither  crack  in 
flattening  nor  run  at  the  edges.  These  pats  are  placed  in  a  vessel 
of  cold  water  immediately  after  gauging  and  heat  applied  and 
regulated  so  that  the  water  boils  in  about  an  hour.  The  boiling 

i  See  page  298. 


SOUNDNESS  465 

is  continued  for  three  hours,  when  the  pats  are  removed  and  ex- 
amined for  checking  and  cracking.  Many  operators  after  steam- 
ing the  pats  for  five  hours  as  prescribed  by  the  standard  rules  and 
noting  the  results  place  the  pats  down  in  the  water  and  boil  for 
from  three  to  five  hours. 

Calcium  Chloride  Test. 

Candlot  discovered  by  a  series  of  experiments  upon  cement 
that  if  the  cement  is  either  gauged  with  or  kept  in  water  contain- 
ing calcium  chloride  the  free  lime  in  it  is  slaked  much  more 
quickly.  The  more  concentrated  the  solution  the  more  marked 
the  effect.  The  action  of  the  salt  is,  therefore,  similar  to  that  of 
heat,  to  increase  the  chemical  action  causing  expansion.  If  the 
cement  is  guaged  with  concentrated  solution  of  calcium  chloride, 
the  lime  will  probably  all  be  slaked  before  the  cement  sets,  so 
that  no  cracking  will  occur  on  hardening,  even  if  much  free  lime 
is  present.  If,  however,  the  calcium  chloride  solution  is  more 
dilute  (40  grams  to  the  liter)  it  will  only  cause  slaking  of  a  very 
small  percentage  of  the  free  lime,  such  a  small  percentage  as  is 
unobjectionable  in  cements.  If  a  pat  made  of  this  mortar  is 
then  kept  in  a  calcium  chloride  solution  of  the  same  strength, 
the  slaking  of  the  rest  of  the  lime  will  be  greatly  hastened  and 
crackling  will  soon  appear  if  a  harmful  quantity  of  free  lime  is 
present.  To  carry  out  the  test,  gauge  the  cement  with  a  4  per 
cent,  solution  (40  grams  to  the  liter)  of  calcium  chloride,  make 
into  pats  upon  glass  plates  and  allow  to  set,  after  which  immerse 
the  pats  in  the  cold  4  per  cent,  solution  of  calcium  chloride  for 
twenty-four  hours  and  then  remove  and  examine  for  cracks, 
softening,  etc. 

Bauschinger's  Calipers. 

The  expansion  or  contraction  of  cement  during  hardening 
may  be  measured  directly  and  very  accurately  by  means  of  Bau- 
schinger's  caliper  apparatus  (Fig.  159).  By  means  of  this  instru- 
ment changes  in  the  length  of  small  parallelopipedons,  100  mm. 
long  and  5  sq.  cm.  cross-section,  may  be  actually  measured  to 
within  1/200  mm.  The  apparatus  consists  of  a  stirrup-shaped 
30 


466 


PORTLAND    CEMENT 


caliper,  having  a  fine  micrometer  screw  on  its  right  arm,  the  left 
being  the  support  of  a  sensitive  lever.  The  shorter  arm  of  this 
lever  terminates  in  a  blunt  caliper  point  and  is  pressed  against 
the  measuring  screw  by  a  spring  attached  to  the  long  arm.  The 
calipers  are  readily  moved  in  any  direction  and  the  micrometer  is 
read  in  the  usual  manner.  One  revolution  of  the  screw  equals  0.5 
mm.  and  the  readings  on  the  head  are  made  at  1/200  mm.  The 


Fig.    159. — Bauschinger's  caliper  apparatus. 

specimen  is  molded  with  square  cavities  in  the  ends,  and  in  these 
are  set  plates  of  glass  containing  centers  for  the  caliper  points. 
The  molding  is  done  similar  to  that  for  tension  specimens  except 
that  both  sides  should  be  repeatedly  struck  off  smooth.  It  re- 
quires but  a  few  minutes  to  measure  a  specimen  by  this  apparatus. 

Le  Chatelier's  Calipers. 

Le  Chatelier's  calipers  are  shown  in  Fig.  160.  This  apparatus 
consists  of  a  small  split  cylinder  of  spring  brass  or  other  suitable 
metal  of  0.5  mm.  (o.oi97-in.)  in  thickness,  30  mm.  (i.i875-ins.) 
internal  diameter,  and  30  mm.  high,  forming  the  mold,  to  which 
on  either  side  of  the  split  are  attached  two  indicators  165  mm. 


SOUNDNESS  467 

(6.5-ins.)  long  from  the  center  of  the  cylinder,  with  pointed  ends 
a,  a,  as  shown  upon  the  sketch. 


El  e  vert-ion. 
Fig.  160.— Le  Chatelier's  calipers. 

This  apparatus  is  used  in  determining  the  soundness  of  ce- 
ment in  Great  Britain,  where  the  standard  specifications1  demand 
that  the  cement  shall  not  show  a  greater  expansion  than  12  mm. 
after  having  been  spread  out  for  a  depth  of  3  inches  and  exposed 
to  the  air  for  24  hours  at  a  temperature  of  58°  to  64°  F.  The 
test  is  to  be  conducted  as  follows : 

The  mold  is  to  be  placed  upon  a  small  piece  of  glass  and  filled 
with  cement  gauged  in  the  usual  way,  care  being  taken  to  keep 
the  edges  of  the  molds  gently  together  while  this  operation  is 
being  performed.  The  mold  is  then  covered  with  another  glass 
plate,  a  small  weight  is  placed  on  this  and  the  mold  is  immediate- 
ly placed  in  water  at  58°  to  64°  F.  and  left  there  for  24  hours. 

The  distance  separating  the  indicator  points  is  then  measured, 
and  the  mold  placed  in  cold  water,  which  is  brought  to  a  boiling 
point  in  15  to  30  minutes,  and  kept  boiling  for  six  hours.  After 
cooling,  the  distance  between  the  points  is  again  measured,  the 
difference  between  the  two  measurements  represents  the  expan- 
sion of  the  cement,  which  must  not  exceed  the  limits  laid  down 
in  the  specification. 

The  writer  has  used  a  form  of  caliper  which  may  be  easily 
made.  This  consists  of  an  ordinary  machinist's  micrometer  cali- 
per which  has  been  cut  in  two  and  extended  to  six  inches  by 
riveting  in  securely  a  piece  of  brass,  in  order  to  allow  the  taking 
of  a  prism  of  this  length.  The  riveting  must  be  so  done  that  the 
caliper  points  will  not  spread  when  pressure  is  applied.  This  is 
accomplished  by  having  the  rivets  fit  the  holes  very  tightly.  The 
caliper  may  be  used  in  either  of  two  ways,  (a)  Pieces  of  glass 

*  Report— Committee  on  Cement,  Engineering  Standards  Committee. 


468  PORTLAND    CEMENT 

plate  are  placed  in  the  cement  prism  so  as  to  serve  as  centers  for 
the  caliper  points  or  (b)  two  small  brass  screws  with  round 
heads  to  which  have  been  soldered  copper  wires  may  be  molded 
in  the  test  pieces  and  these  attached  to  a  battery  and  sounder. 
When  the  caliper  points  touch  the  screws  on  both  sides  of  the 
prism,  electrical  connection  is  established,  which  causes  the  sound- 
er to  buzz. 

Microscopic  Test  for  Free  Lime. 

Prof.  Alfred  D.  White  proposes1  a  microscopic  test  for  free 
lime.  Unfortunately  this  test  does  not  differentiate  between  cal- 
cium oxide  which  causes  unsoundness  and  calcium  hydrate  which 
is  developed  in  cement  on  storage  and  seasoning  of  either  the 
clinker  or  the  cement  itself.  As  all  cement  contains  calcium 
hydrate  to  the  extent  of  from  2  to  5  per  cent,  and  even  more 
when  it  reaches  the  consumer  the  test  is  of  no  value  to  the 
latter  to  determine  unsoundness.  In  scientific  investigations  at 
the  plant  on  freshly  burned  and  ground  clinker  the  test  will  be 
found  of  some  use. 

The  method  is  based  on  the  formation  on  the  slide  of  the 
microscope  of  a  characteristic  crystalline  calcium  phenolate  readi- 
ly recognizable  in  polarized  light.  The  reagent  is  prepared  by 
dissolving  crystallized  phenol  in  an  immiscible  and  rather  non- 
volatile solvent  and  adding  a  trace  of  water.  The  method  of 
preparation  preferred  by  the  author  is  to  dissolve  5  grams  of 
phenol  in  5  cc.  nitrobenzol  and  add  to  this  solution  two  drops 
of  water.  Instead  of  nitrobenzol,  alpha  brom-naphthalene  may 
be  used,  and  is  for  some  reasons,  notably  its  lower  volatility,  to 
be  preferred.  It  does  not,  however,  give  such  sharp  results  as 
nitrobenzol. 

In  making  this  test  about  two  or  three  milligrams  of  the  finely 
powdered  material  are  placed  in  the  center  of  a  microscope  slide, 
a  drop  of  reagent  put  upon  it  and  then  a  cover  glass,  which  is 
pressed  down  and  rubbed  gently  to  and  fro  till  the  cement  spreads 
itself  out  somewhat.  It  is  advisable  not  to  spread  the  cement  out 
too  thinly  but  to  leave  a  thick  nucleus  where  the  crystals  will 
first  appear,  and  to  have  the  thickness  decrease  toward  the  edges. 

!/.  Jnd.  and  En g.  Chem.,  Jan.,  1909. 


Fig.  161. — Microscopic  test  for  free  lime. 


Fig  .162. — Microscopic  test  for  free  lime. 


SOUNDNESS  469 

The  slide  is  now  observed  in  a  polarizing  microscope  with  the 
nicols  crossed,  or  if  easier  for  the  eye,  with  the  polarizer  rotated 
slightly.  Prof.  White  recommends  a  two-thirds  inch  objective 
and  one  inch  eye-piece  giving  a  magnification  of  about  80. 

The  phenomena  appearing  when  pure  lime  alone  is  being  ob- 
served will  first  be  described.  When  the  freshly-prepared  slide 
is  put  on  the  microscope  the  lime  being  isotropic  is  almost  in- 
visible and  the  whole  field  is  dark.  Within  a  few  minutes  the 
edges  of  the  fragments  of  lime  begin  to  show  brilliant  points  which 
in  a  quarter  of  an  hour  develop  into  brilliant  clusters  of  radiating 
needles  as  shown  in  Fig.  161  which  is  a  photomicrograph  of  a 
commercial  cement.  On  account  of  the  great  contrast  in  il- 
lumination between  the  brilliantly  refracting  calcium  phenolate 
and  the  feebly  refracting  cement  the  photomicrograph  shows  noth- 
ing but  the  calcium  phenolate  crystals  and  does  not  show  these 
sharply  since  their  strong  double  refraction  makes  them  appear 
to  be  surrounded  by  a  halo.  The  eye  of  the  observer  at  the 
microscope  can  readily  discern  the  individual  crystals  forming 
what  are  only  blotches  of  white  in  the  photograph.  If  the  lime 
fragments  are  crowded  too  closely  together  on  the  slide  the 
crystals  interlace  so  that  their  structure  cannot  be  noted.  These 
crystals  grow  till  in  the  course  of  a  couple  of  hours  they  may  be 
o.i  mm.  long.  Very  little  further  change  is  noticeable  for  six 
hours  but  in  twenty-four  hours  the  nitrobenzol  will  have  largely 
evaporated  and  the  crystals  may  have  entirely  disappeared.  Con- 
fusion from  formation  of  crystals  of  phenol  has  never  been  ob- 
served by  White,  the  moisture  present  in  the  reagent  or  absorbed 
from  the  air  probably  preventing  the  phenol  from  crystallizing 
when  the  solvent  evaporates. 

Hydrated  calcium  oxide  gives  needles  similar  to  the  oxide, 
but  they  generally  form  more  rapidly  and  are  finer.  On  the 
other  hand,  the  crystals  formed  from  lime  which  has  been  fused 
in  the  electric  arc  have  a  different  form.  Instead  of  straight 
needles  the  crystals  appear  as  plumes  or  feathery  petals  which 
in  favorable  cases  give  the  group  somewhat  the  appearance  of  a 
chrysanthemum.  Something  of  this  appears  in  Fig.  162  where 
the  dark  nucleus  in  the  upper  group  shows  the  granule  of  free 


47O  PORTLAND    CEMENT 

lime  from  which  the  plume-like  crystals  grow.  No  substance 
other  than  calcium  oxide  or  hydroxide  has  been  found  to  give 
this  reaction. 

OBSERVATIONS. 
Importance  of  the  Test. 

The  most  important  quality  of  cement  is  soundness,  for  no 
matter  how  high  a  degree  of  tensile  strength  a  cement  may  de- 
velop at  comparatively  short  periods,  if  it  fails  to  resist  the  dis- 
integrating influences  of  the  atmosphere  or  the  water  in  which  it 
may  be  placed,  it  is  useless  as  a  material  of  construction.  This 
tendency  to  disintegrate,  fall  to  a  powder,  crack  or  expand  on 
mixing  the  cement  with  water  is  termed  "blowing."  This  fault 
is  usually  due  to  improper  proportioning  of  the  raw  materials,  al- 
lowing an  excess  of  lime  over  what  will  combine  with  the  silica 
and  alumina  of  the  cement  mixture ;  or  an  improper  burning,  fail- 
ing to  raise  the  temperature  to  the  point  where  all  the  lime  may 
combine  with  the  silica  and  alumina,  thus  leaving  some  in  the  un- 
combined  state;  or  from  insufficient  grinding  of  the  raw  mate- 
rials for  the  lime  to  unite  with  the  silica  and  alumina.  This  free 
or  .loosely  combined  lime  on  coming  in  contact  with  water  is 
slacked  and  expands,  causing  the  cement  to  crack  and  fall  to 
pieces. 

Causes  of  Unsoundness. 

Some  discussion  has  been  aroused  of  late  as  to  what  causes  the 
failure  of  cement  to  stand  the  various  tests  for  soundness.  Some 
of  the  various  compounds  which  may  be  present  in  cement,  cal- 
cium di-silicate,  alkalies,  etc.,  are  said  to  promote  checking  in  the 
boiling  test.  All  authorities  seem  to  agree,  however,  that  the 
chief  cause  is  the  presence  of  free  or  unstable  lime  over  and  above 
a  certain  limit.  This  free  lime  slakes  after  the  cement  has  itself 
hardened  or  set,  causing  the  test  piece  to  warp  and  check  from 
the  expansion  set  up  by  the  change.  The  object  of  all  tests  for 
soundness  is,  therefore,  to  ascertain  if  the  maximum  of  free  lime 
that  may  safely  be  present  has  been  exceeded. 

A  certain  small  percentage  of  free  lime  is  present  in  all  ce- 
ment. I  have  frequently  added  as  much  as  5  per  cent,  of  un- 
slaked lime  (prepared  from  precipitated  calcium  oxalate,  and 


SOUNDNESS 


471 


hence  very  finely  pulverized)  to  cement,  and  yet  pats  made  from 
the  mixture  passed  both  boiling  and  28  day  tests.  If  the  lime  is 
coarser,  the  quantity  which  can  be  added  is  much  smaller. 
Slaked  lime  may  be  added  in  large  quantities  without  affecting 
either  boiling  or  cold  water  pats ;  so  may  also  carbonate  of  lime. 
Pats  with  any  proportion  of  either  are  perfectly  sound.  Hy- 
drated  lime  (mechanically  slated  lime)  is  now  added  to  con- 
crete extensively  for  water-proofing  the  latter.  No  fears  need 
be  experienced  that  such  concrete  will  fail. 

Effect  of  Seasoning  on  Soundness. 

Anything  which  promotes  the  changing  over  of  the  free  lime 
into  slaked  lime  or  carbonate  of  lime  will  cause  cement  at  first 
unsound  to  become  sound.  The  air  always  contains  the  ele- 
ments, moisture  and  carbon  dioxide,  to  bring  about  such  a 
change,  so  that  if  cement  that  is  unsound  is  stored  for  any  length 
of  time  it  will  gradually  become  sound,  from  the  slaking  and  car- 
bonating  of  the  free  lime.  This  is  illustrated  by  the  following 
table : 

TABLE  XLV.— SHOWING  EFFECT  OF  SEASONING  ON  SOUNDNESS. 


Age  in  days 
after  being 
ground1 

Cement 

No.  i 

Cement 
No.  2 

Cement 
No.  3 

Cement 

No.  4 

Cement 
No.  5 

Results  of  5  hour  steam  test  (A.  S.  C.  It) 

Partly 

Entirely 

0 

Checked 

disinte- 

Checked 

Checked 

disinte- 

I 

Checked 

grated 

Badly 
checked 

Checked 

0.  K. 

grated 
Entirely 
disinte- 
grated 

Partly 

Slightly 

Badly 

Slightly 

disinte- 

checked 

checked 

checked 

grated 

7 

0.  K. 

Checked 

Slightly 
checked 

Badly 
checked 

H 



Checked 

0.  K. 

Badly 
checked 

21 

Slightly 
checked 



Checked 

28 

O    K 

Checked 

90 

O.  K. 

1  Samples  were  seasoned  in  a  small  paper  bag  on  a  shelf  in  the  laboratory. 


472 


PORTLAND    CEMENT 


Cement  which  has  seasoned  sound  is  just  as  good  as  one  which 
was  sound  when  freshly  made,  and  the  writer  does  not  think  the 
engineer  need  concern  himself  whether  the  manufacturer  prefers 
to  make  cement  which  is  sound  when  fresh,  or  whether  he  pre- 
fers to  age  it  sound  in  his  stock-house.  So  long  as  it  is  sound 
he  is  secure,  and  possibly  the  softer  burned  clinker,  usually  un- 
sound when  freshly  ground,  will  grind  with  a  greater  percentage 
of  flour,  increasing  the  sand  carrying  capacity  of  the  cement. 

Effect  of  Fine  Grinding  of  the  Raw  Materials  on  Soundness. 

In  order  for  cement  to  stand  the  boiling  test  when  fresh  from 
the  grinding  mills,  the  raw  materials  must  be  finely  ground.  The 
unsoundness  due  to  coarse  grinding  of  the  raw  materials  is  prob- 

TABLE  XLVI.— SHOWING  EFFECT  OF  FINENESS  OF  GRINDING  OF 
CLINKER  ON  SOUNDNESS. 


Condition  of  cement  as  tested 

Fineness 

Result  of 
5  hours  steam  test 
(A.  S.  C.  E.) 

Residue 
No.  100 

Residue 
No.  200 

As  received  from  the  mills,  tested 

8-5 

8.5 
8.5 
o.o 
o.o 

0.0 

27.0 
27.0 
27.0 
0.0 

o.o 

0.0 

Partially  disintegrated 
Partially  disintegrated 
Badly  checked 
Sound 
Slightly  checked 

Sound 

As  received  from  the  mills,  tested 
again  after  seasoning  one  week  • 
As  received  from  the  mills,  tested 
again  after  seasoning  one  month 
Portion  of  sample  passing  No.  200 
sieve  tested  one  day  old  •  •  • 

Sample  ground  to  all  pass  a  No. 
200  sieve,  tested  one  day  old  •  •  . 
Sample  ground  to  all  pass  a  No. 
200  sieve,  tested  one  week  after 

ably  the  hardest  form  of  unsoundness  to  cure  by  aging.  This  is 
particularly  so  if  the  clinker  has  been  burned  very  hard,  as  the 
coarse  pieces  of  limestone,  calcined  to  free  lime,  are  locked  up  in 
a  case  of  clinker.  If  this  case  is  not  broken  in  grinding,  the 
free  lime  is  left  surrounded  by  a  wall  of  clinker  and  will  be  very 
slowly  acted  upon  by  the  moisture  of  the  air.  The  experiment  in 
Table  XLVI  seems  to  prove  this  very  thing.  Laboratory  records 
show  the  unsoundness  of  this  sample  to  have  been  due  to  coarse 


SOUNDNESS  473 

grinding  or  the  raw  mixture.  The  fine  particles  passed  the  boil- 
ing test  fresh,  the  coarse  ones  failed  even  on  grinding,  but  on 
aging  one  week,  the  ground  particles  stood  the  test.  Aging  the 
cement,  however,  for  two  weeks  failed  to  make  it  sound,  because 
the  free  lime  was  locked  up  in  the  coarse  particles,  where  hydra- 
tion  could  only  take  place  very  slowly,  but,  on  grinding  the 
coarse  particles,  the  air  had  a  chance  to  get  at  the  free  lime  and 
convert  it  to  the  innocuous  hydroxide.1  The  effect  of  fine  grind- 
ing of  the  cement  itself  on  soundness  has  been  discussed  in 
Chapter  XV. 

Effect  of  Sulphates  on  Soundness. 

Pats  allowed  to  harden  in  steam  or  hot  water  will  often  pass 
the  boiling  test  where  pats  hardened  in  air  will  not.  It  must  be 
remembered  that  checking  is  caused  by  slaking  after  the  pats  are 
fully  hardened.  If  they  are  placed  in  steam  to  harden  the  moist 
air  merely  accelerates  the  slaking  of  the  lime,  doing  the  work  be- 
fore the  pat  hardens,  just  as  heat  hastens  any  chemical  action. 
The  addition  of  sulphates,  either  as  gypsum  or  plaster  of  Paris, 
aids  the  cement  in  standing  the  boiling  test,  probably  because  it 
delays  the  set  until  after  the  lime  has  slaked.  The  rendering  of 
the  free  lime  inert  by  the  formation  of  compounds  with  the  lime 
by  the  gypsum  seems  hardly  probable,  since  the  lime  and  gypsum 
could  not  react  unless  both  were  in  solution,  and  if  the  water 
could  get  at  the  free  lime  to  dissolve  it,  slaking  would  take  place 
on  adding  water  only,  and  the  harmless  hydroxide  would  be 
formed.  The  early  hardness  due  to  gypsum  can  hardly  play  any 
part,  since  cements  breaking  as  high  as  600  pounds  in  24  hours 
may  fail  on  the  boiling  test,  while  briquettes  breaking  at  150 
pounds  may  be  sound.  My  own  experiments  go  to  show  that 
anything  which  will  delay  the  setting  of  cement  until  after  the 
free  lime  has  slaked,  or  that  will  hasten  the  slaking  of  the  free 
lime  before  the  pat  sets,  will  make  cement  sound. .  The  table 
given  below  shows  the  effect  of  additions  of  plaster  on  the  boil- 
ing test : 

1  See  also  Taylor,  Proceedings  Am.  Soc.  Test.  Mat.,  III..  (1903),  377,  and  Butler,  Port- 
land Cement,  p.  174. 


474 


PORTLAND 


TABLE  XLVII.— SHOWING  EFFECT  OF  ADDITIONS  OF  GYPSUM  OR 
PLASTER  OF  PARIS  ON  SOUNDNESS. 


Sample 

Per  cent. 
SO3 

Result  of  5  hour  steam  test  (A.  S.  C.  E.)1 

0.5  per  cent, 
plaster  added 

i.o  per  cent, 
plaster  added 

2.0  per  cent, 
plaster  added 

3.0  per  cent, 
plaster  added 

1.  21 

1-43 
1.18 

1.36 
0.31 

Sound 
Checked 
Checked 
Checked 
Checked 

Sound 
Checked 
Checked 
Checked 

Sound 
Checked 
Sound 

Sound 

Ground  clinker 

Value  of  Accelerated  Tests. 

At  the  1903  meeting  of  the  American  Society  for  Testing  Ma- 
terials, Mr.  W.  P.  Taylor,  of  the  Philadelphia  Municipal  Testing 
Laboratory,  read  a  very  carefully  prepared  paper  upon  the  boil- 
ing test2  in  which  he  compared  the  results  of  neat  briquettes  and 
neat  pats  with  the  results  of  the  boiling  test.  As  is  usual,  he 
considered  a  falling  off  of  the  strength  of  neat  briquettes  on  long 
time  tests  and  a  cracking  and  warping  of  the  neat  cold  water  pat 
as  being  positive  evidence  of  the  presence  of  injurious  constit- 
uents in  the  cement.  He  gives  these  figures:  "Of  all  the  sam- 
ples failing  to  pass  the  boiling  test  34  per  cent,  of  them  developed 
checking  or  curvature  in  the  normal  pats  or  a  loss  of  strength  in 
less  than  28  days.  Of  those  samples  that  failed  in  the  boiling 
test  but  remained  sound  for  28  days,  3  per  cent,  of  the  normal 
pats  showed  checking  or  abnormal  curvature  in  2  months,  7  per 
cent,  in  3  months,  10  per  cent,  in  4  months,  26  per  cent,  in  6 
months,  and  48  per  cent,  in  one  year ;  and  of  these  same  samples 
37  per  cent,  showed  a  falling  off  in  tensile  strength  in  2  months, 
39  per  cent,  in  3  months,  52  per  cent,  in  4  months,  63  per  cent, 
in  6  months,  and  71  per  cent,  in  one  year.  Or  taking  all  these 
together,  of  all  the  samples  that  failed  in  the  boiling  test  86  per 
cent,  of  them  gave  evidence  in  less  than  a  year's  time  of  possess- 
ing some  injurious  quality. 

"On  the  other  hand,  of  those  cements  passing  the  boiling  test 

1  All  samples  were  unsound  without  addition  of  plaster  of  Paris. 

2  Proceedings  Amer.  Soc.  Test.  Mat.,  III.,  (1903),  374. 


SOUNDNESS  475 

but  one-half  of  i  per  cent,  gave  signs  of  failure  in  the  normal 
pat  tests  and  but  13  per  cent,  showed  a  falling  off  in  strength 
in  a  year's  time." 

It  is  unfortunate  that  the  test  which  seems  to  be  accepted  by 
the  majority  as  a  standard  is  the  long  time  cold  water  pat,  a  test 
requiring  such  length  of  time  for  its  completion  as  to  practically 
forbid  its  use.  The  conditions  of  the  case  demand  a  rapid  test  in 
order  that  the  consumer  may  not  be  required  to  store  the  cement 
for  a  long  period  of  time  while  he  awaits  the  results  of  his  cold 
water  pats. 

To  the  manufacturer  the  steam  and  boiling  tests  are  exceeding- 
ly useful,  for  if  a  cement  will  pass  these  tests  it  will  pass  any  test 
to  which  it  may  be  subjected.  He  can  not  hold  his  cement  in  his 
stock-house  for  months  while  he  ascertains  if  it  will  pass  the  cold 
water  pat  test  and  so  he  applies  an  accelerated  test  to  tell  him  if 
this  cement  will  pass  the  tests  to  which  it  is  likely  to  be  put.  To 
my  mind  there  is  a  strong  comparison  between  the  steam  test  and 
the  color  test  for  carbon,  so  much  used  in  the  steel  works  labora- 
tories. While  this  latter  test  is  very  useful  to  the  manufacturer 
still  no  engineer  would  condemn  steel  on  the  result  of  such  a  test, 
for  though  it  may  give  correct  results  in  nine  out  of  ten  cases  he 
does  not  care  to  take  the  risk  of  this  being  the  tenth  case  and  of 
throwing  out  a  good  steel,  and  so  working  great  hardship  to  the 
manufacturer. 

Unquestionably  much  good  concrete  has  been  made  from  so- 
called  unsound  cement,  and  this  is  the  key  to  the  whole  objection 
to  the  hot  test.  It  is  probable  that  much  of  the  first  American 
Portland  cement  would  not  have  passed  the  steam  test,  yet  it  is 
upon  the  merits  of  the  work  done  with  this  cement  that  engineers 
are  now  using  American  instead  of  imported  cement.  Butler 
gives  a  strong  plea  for  the  Faija  test  and  states  that  in  the  twenty 
years  this  test  has  been  in  use,  no  cases  of  failure  in  work  by  ce- 
ment passing  this  test  have  come  under  his  observation.  If  the 
Faija  test  is  severe  enough  to  exclude  all  bad  cements,  then  the 
boiling  tests  is  needlessly  severe  as  it  rejects  many  cements  which 
pass  Faija's  test. 


476  PORTLAND    CEMENT 

All  cement  probably  contains  some  free  lime.  From  the  nature 
of  the  case  this  must  be  so,  since  cement  raw  materials  are  not 
ground  to  a  degree  of  fineness  nor  carried  to  a  state  of  fusion 
which  would  permit  of  every  molecule  of  lime  coming  in  contact 
with  a  molecule  of  silica  or  of  alumina.  Now  there  are  limits  be- 
yond which  if  the  uncombined  or  free  lime  goes,  certain  results 
will  take  place.  Let  us  suppose  that  with  a  very  small  percentage 
present  the  cement  will  fail  on  the  boiling  test  but  pass  satisfac- 
torily five  hours  in  steam,  and  if  a  still  larger  percentage  is  pres- 
ent it  will  fail  in  the  steam  but  pass  the  Faija  test.  Now,  again, 
let  us  suppose  that  a  neat  mixture  with  a  certain  small  percentage 
of  free  lime  is  sound,  with  a  larger  percentage  a  3 :  i  sand  mixture 
is  sound,  with  a  still  larger  percentage  a  1:3:8  concrete  is  sound. 
(It  is  well  understood  that  the  tendency  of  cement  to  disintegrate 
is  greater  in  a  neat  paste  than  in  a  sand  mixture,  and  anyone  with 
experience  in  cement  testing  knows  of  cases  where  neat  bri- 
quettes were  disintegrated  in  time  and  yet  the  sand  ones  were 
sound  and  strong.)  Now  how  do  we  know  that  the  limit  of  lime 
which  may  be  present  in  good  cement  (that  is  cement  which  will 
make  enduring  concrete)  is  coincident  with  that  maximum  which 
may  be  present  for  a  sound  boiling  test  ? 

Nearly  all  advocates  of  the  steam  test  have  tried  to  prove  these 
two  limits  coincident  by  comparing  the  steam  test  with  the  results 
of  neat  pats  and  neat  briquettes.  Usually  the  coincidence  of  a 
failure  on  the  boiling  test  with  either  a  warping  or  cracking  of 
the  neat  pats  or  a  loss  of  strength  in  the  neat  briquettes  on  long 
time  tests  is  considered  competent  evidence  in  favor  of  the  boil- 
ing test.  In  reality  cement  is  seldom  used  neat.  A  cement  which 
fails  on  the  boiling  test,  whose  neat  briquettes  fall  off  in  strength 
after  7  or  28  days,  yet  whose  sand  briquettes  increase  in  strength 
as  they  grow  older,  has  certainly  given  evidence  that  it  will  make 
good  concrete.  In  weighing  evidence  for  any  test  it  must  be  re- 
membered that  we  do  not  make  the  soundness  test  to  see  if  neat 
briquettes  will  fail  in  strength  as  they  age  or  if  neat  pats  will 
warp  and  decay,  but  whether  sidewalks,  piers,  abutments,  founda- 
tions, walls,  floors  and  buildings  of  concrete,  not  neat  cement,  will 


SOUNDNESS  477 

be  permanent,  and  the  thing  therefore  to  compare  the  boiling  test 
with,  is  concrete.  Not  until  we  can  compare  our  laboratory  re- 
cords with  many  examples  of  both  failures  and  successes  in  actual 
work  will  we  have  reliable  data  for  forming  our  conclusions 
as  to  the  reliability  of  the  various  tests  for  soundness. 

Experiments  made  by  a  committee  of  the  Society  of  German 
Portland  Cement  Manufacturers  in  connection  with  the  Royal 
Testing  Laboratory  at  Charlottenburg  forced  them  to  report  in 
1900  and  again  in  1903  that  none  of  the  so-called  accelerated 
tests  for  consistency  of  volume  was  adapted  to  furnish  a  reliable 
and  quick  judgment  in  all  cases  concerning  the  applicability  of  a 
cement.  The  experiments  which  they  made  consisted  in  putting 
the  cement  into  actual  work  and  observing  it  during  a  period  of 
four  years.  The  committee  recommended  the  28  day  cold  water 
pat  as  a  standard  test.  If  this  test  is  taken  as  a  standard  the  hot 
test  will  reject  two  good  cements  for  every  bad  one. 


MISCELLANEOUS. 


Chapter  XIX. 


THE  DETECTION  OF  ADULTERATION  IN  PORTLAND 
CEMENT. 


Cements  are  adulterated  with  natural  cement,  blast-furnace 
slag,  ground  limestone,  shale,  ashes,  etc.  Some  of  these  sub- 
stances are  so  similar  to  Portland  cement  that  chemical  analysis 
fails  to  show  their  presence.  It  is,  therefore  necessary  to  direct 
special  tests  to  their  detection.  When  present  in  small  quantities, 
it  is  probable  that  even  such  tests  will  fail  to  show  positively  an 
adulterated  cement. 

Tests  of  Drs.  R.  and  W .  Fresenius. 

Drs.  R.  and  W.  Fresenius/  at  the  request  of  the  Association  of 
German  Cement  Manufacturers,  made  investigations  into  the  sub- 
ject of  cement  adulteration  looking  to  a  method  of  detecting  the 
same.  They  experimented  upon  twelve  samples  of  pure  Portland 
cement  from  Germany,  England  and  France,  and  compared  the 
results  of  tests  upon  these  with  the  results  obtained  by  similar 
tests  upon  three  kinds  of  hydraulic  lime,  three  kinds  of  weathered 
slag,  and  two  of  ground  slag.  The  cements  were  of  various  ages 
and  had  been  exposed  to  the  air  for  various  lengths  of  time.  On 
the  next  page  are  tabulated  their  experiments  for  comparison. 

Proposed  Tests. 

As  the  result  of  these  experiments  they  proposed  the  following 
tests  for  the  detection  of  adulteration: 

1.  The  specific  gravity. 

This  must  not  be  lower  than  3.10. 

2.  The  loss  on  ignition. 

1  Ztschr.  anal.  Chem.,  23,  175,  and  24,  66. 


DETECTION  AND  ADULTERATION  IN  PORTLAND  CEMENT        479 


This  should  be  between  0.3  and  2.59  per  cent.;  certainly  not 
much  more. 

3.  The   alkalinity   imparted   to    water.     0.5    gram   of   cement 
should  not  render  50  cc.  of  water  so  alkaline  as  to  require  more 
than  6.25  cc.  nor  less  than  4  cc.  of  decinormal  acid  to  neutralize. 

4.  The  volume  of  normal  acid  neutralized. 

One  gram  of  cement  should  neutralize  from  18.8  to  21.7  cc.  of 
normal  acid. 

5.  The  volume  of  potassium  permanganate  reduced. 

One   gram   of   cement    should   reduce   not   much   more   than 
0.0028  gram  of  potassium  permanganate. 

TABLE  XLVIIL— ADULTERATION  IN  PORTLAND  CEMENT. 


i 

2 

3 

4 

5 

1^2 

-•g 

d" 

4«i 

| 

| 

g_bVc3 

2*2 

c  ^ 

cd 

Description 

2 

'1 

«+*  3  *• 

•M    C 

O 

be 

00 

•~                Q 

ova 

o  o 

"0*2 

£ 

1 

1 

III 

|2~ 

"3  *-G 

P 

111 

Per  cent. 

5 

cc. 

rug. 

mg. 

Portland  cement,  A  

3-155 

1.58 

6.25 

20.71 

0.79 

•4 

B.... 

3-125 

2.59 

4.62 

21.50 

2.38 

.6 

c.... 

3-155 

2.  II 

4.50 

20.28 

0-93 

.8 

D-... 

3-144 

I.98 

5.10 

21.67 

1.  12 

.0 

'             '          E 

3.144 

1.25 

6.12 

19.60 

0.98 

.6 

?'.'.'.'. 

3-134 

2.04 

4-95 

20.72 

1.  2  1 

.1 

1            "         G  

3-144 

0.71 

4-30 

22.20 

0.89 

o.o 

H-... 

3-125 

I.  II 

4-29 

20.30 

1.07 

0.7 

J.... 

3-134 

I.OO 

4.00 

19.40 

2.01 

o.o 

K-... 

3-144 

0-34 

4.21 

20.70 

0.98 

o.o 

'            "         L  

3-154 

i-49 

4.60 

18.80 

2.80 

0.3 

M.-.. 

3.125 

1-25 

5-5o 

20.70 

2-33 

0.0 

Hvdraulic  lime      A  

2.441 

18.26 

20.23 

21-35 

1.40 

27.8 

'      «            "         B  

2.551 

17.82 

22.73 

26.80 

0.93 

31.3 

c.-.. 

2.520 

19.60 

19.72 

19.96 

0.98 

47.7 

Weathered  slag     A  

3.012 

0.76 

0.91 

14.19 

74.60 

3-6 

*             "          B-  •  •  ' 

3-003 

1.92 

0.70 

13-67 

60.67 

3-5 

c.... 

2.967 

I.IT 

I.OO 

9.70 

44-34 

2-9 

Ground  slag             I  

3-003 

0.32 

0.31 

64.40 

2-4 

"       "              II.... 

2.873 

0.43 

O.II 

8.20 

73.27 

2.2 

480  PORTLAND    CEMENT 

6.  The  weight  of  carbon  dioxide  absorbed. 

Three  grams  of  cement  should  not  absorb  more  than  0.0018 
gram  of  carbon  dioxide. 

The  tests  I,  3,  4,  and  5  are  for  the  detection  of  slag  and  i,  2, 
3  and  6  for  the  detection  of  hydraulic  lime. 

Drs.  R.  and  W.  Fresenius  also  tried  these  tests  upon  experi- 
mental mixtures  containing  10  per  cent,  of  slag  or  hydraulic  lime, 
and  in  each  case  were  able  to  detect  the  impurity. 

Carrying  Out  the  Tests. 

The  methods  employed  for  carrying  out  the  tests  were  as  fol- 
lows: 

1.  They  used  for  taking  the  specific  gravity  the  method  of 
Schumann  (see  page  368),  with  turpentine  as  the  liquid.  The  end 
of  the  tube  was  corked  to  prevent  evaporation,  the  temperature 
kept  constant,   and  the  vessel   carefully   shaken  to  displace  air 
bubbles.     Le  Chatelier's  apparatus  would  answer  as  well,  how- 
ever, with  kerosene  for  the  liquid. 

2.  For  the  loss  on  ignition,  2  grams  of  cement  were  weighed 
into  a  tarred  crucible,  and  then  heated  over  a  Bunsen  burner  for 
twenty  minutes.     The  loss  shown  on  again  weighing  was  the  loss 
on  ignition. 

3.  For  the  "alkalinity  to  water  test."     The  substance  was  finely 
powdered  and  passed  through  a  sieve  of  5,000  meshes  to  the 
square  centimeter.1    Of  the  resulting  powder,  i  gram  was  shaken 
up  with  loo  cc.  distilled  water  without  warming  for  ten  min- 
utes.    The  solution  was  then  passed  through  a  dry  filter-paper 
into  a  dry  vessel  and  50  cc.  of  the  filtrate  titrated  with  decinormal 
hydrochloric  acid.2 

4.  For  "standard  acid  necessary  to  decompose."     One  gram 
of  the  fine  powder  obtained  in  3  was  shaken  with  30  cc.  of  nor- 
mal hydrochloric  acid3  and  70  cc.  of  water  for  ten  minutes,  with- 

1  32.260  meshes  to  the  square  inch.     The  standard  200  mesh  sieve  will  answer, 

2  To  make  decinormal  hydrochloric  acid,  refer  to  page  315,  with  the  notes  under  this 
section,  and  taking  such  a  quantity  of  dilute  hydrochloric  acid  as  contains  3.65  grams  of 
HC1,  dilute  this  volume  to  I  liter.    Check  its  value  by  one  of  the  methods  given  in  the  sec- 
tion referred  to.    The  2/6  N  nitric  acid  may  be  diluted  to  1/10  N  strength  and  used  in  place 
of  the  */io  N  hydrochloric  acid. 

3  Normal  acid  should  contain  36.5  grams  HC1  per  liter. 


DETECTION  AND  ADULTERATION  IN  PORTLAND  CEMENT        481 

out  warming,  and  filtered  through  a  dry  filter-paper  50  cc.  of  the 
filtrate  were  then  titrated  with  normal  caustic  soda.1 

5.  For  the  volume  of  permanganate  reduced.     One  gram  of 
the  fine  powder,  obtained  in  3,  was  treated  with  a  mixture  of  50 
cc.  of  dilute  sulphuric  acid  (sp.  gr.  1.12)  and  100  cc.  of  water. 
The  resulting  solution  was  then  titrated  with  potassium  perman- 
ganate solution.2 

6.  For  carbon  dioxide  absorbed,  about  3  grams  of  the  fine 
powder  obtained  as  in  3,  were  placed  in  a  weighed  tube  and  a 
stream  of  carbon  dioxide  allowed  to  pass  over  it.    The  sample  was 
then  dried  in  a  desiccator  over  sulphuric  acid  (sp.  gr.  1.184)  and 
weighed.     The  increase  in  weight  gave  the  amount  of  carbon 
dioxide  absorbed,  a  small  calcium  chloride  drying  tube  was  placed 
after  the  tube  containing  the  cement  to  absorb  any  water  evolved. 

Le  Chatelier's  Test. 

Le  Chatelier  has  devised  a  very  neat  test  for  the  adulteration 
in  cement,  depending  upon  the  lower  density  of  the  adulterant 
than  of  the  cement.  His  method  consists  in  separating  these 
lighter  impurities  from  the  cement  by  means  of  a  heavy  liquid, 
a  mixture  of  methyl  iodide  and  benzine,  prepared  of  such 
strength  that  they  float  upon  its  surface  while  the  pure  Portland 
sinks  to  the  bottom. 

This  method  is  in  use  in  the  Philadelphia  City  Testing  Labora- 
tory and  gives  good  satisfaction  there,  where  it  is  used  to  detect 
additions  of  Rosendale  to  Portland  cement.3 

Preparation   of  the  Heavy  Liquid. 

As  the  first  step  the  methyl  iodide  solution  must  be  prepared. 
This  should  be  of  density  2.95  according  to  Le  Chatelier.  As  the 
density  of  the  methyl  iodide  itself  is  3.1,  benzine  must  be  added 

1  To  prepare  normal  caustic  soda,  refer  to  page  314.  and  using  the  above  normal  acid  as 
a  standard  proceed  as  directed  there.  The  -I6  N  solutions  used  in  checking  the  per  cent, 
of  lime  in  cement  mixture  (see  page  232)  mav  be  used  for  this  test.  In  this  case  shake  up 
in  cement  with  a  mixture  of  75  cc.  of  '-'5  normal  acid  and  25  cc.  of  water,  and  titrate  back 
with  the  2/s  normal  alkali. 

-  Dissolve  o  28  gram  of  KMnO4  in  100  cc.  of  water.  Not  much  more  than  i  cc.  of  this 
solution,  or  2  cc.  of  the  solution  used  to  determine  ferric  oxide  in  cement  should  be 
required  if  the  cement  is  unadulterated. 

3  Taylor,  Chem.  Eng.,  I.,  258. 
31 


482 


PORTLAND    CEMENT 


in  small  quantities  until  a  crystal  of  aragonite  (serving  as  a 
guide)  whose  density  is  2.94  just  remains  at  the  surface.  Since 
very  small  quantities  of  benzine  change  the  density  of  the  methyl 
iodide  considerably  it  is  well  to  make  two  solutions,  one  a  little 
above  and  one  a  little  below  the  density  sought,  and  then  to  add 
the  one  to  the  other  until  the  required  density  is  obtained.  By 
this  means  a  more  gradual  change  is  affected  and  the  danger  of 
over-running  the  mark  is  lessened. 

Apparatus. 

Le  Chatelier  used  in  his  experiments  a  little  glass  tube  10  mm. 
in  diameter  and  70  mm.  long.  The  tube  (Fig.  163)  is  widened  at 
the  top  to  a  funnel  and  drawn  at  the  bottom  with  a  regular  slope 
to  an  opening  of  I  mm.  diameter.  This  opening  is  closed  on  the 
interior  a  little  above  the  bottom  by  a  plunger  consisting  of  a 

O 


T 


Fig.  163. — Separatory  funnel  for  methyl  iodide  solutions. 

small   emery  ground-glass   stopper   on   the  end  of  a   glass   rod 
which  projects  above  the  funnel  top. 

Test. 

To  make  a  test  the  stopper  is  wet  with  water  or  glycerine  to 
make  a  tight  joint  and  inserted  into  the  opening  of  the  tube. 
Grease  cannot  be  used  as  it  is  dissolved  by  the  methyl  iodide  so- 
lution. Ten  grams  of  the  suspected  cement  are  weighed  into  the 
tube  and  5  cc.  of  methyl  iodide  solution  (sp.  gr.  2.95),  prepared 
as  above,  poured  upon  it.  A  thin  platinum  wire  bent  into  a  loop 
around  the  plunger  is  then  moved  around  and  up  and  down  in 


DETECTION  AND  ADULTERATION  IN  PORTLAND  CEMENT        483 

the  liquid  in  a  lively  manner  in  order  to  drive  out  all  bubbles 
and  mix  the  cement  and  liquid  thoroughly.  The  apparatus  is  now 
set  aside  for  an  hour,  when  it  will  be  found  that  the  slag  is  on 
top  and  the  cement  below.  The  apparatus  is  now  placed  over  a 
dry  filter,  the  stopper  raised  and  the  cement  and  part  of  the  liquid 
allowed  to  run  out.  The  cement  is  retained  upon  the  filter  while 
the  liquid  is  caught  in  a  vessel  below  and  may  be  used  again. 
The  slag  and  the  rest  of  the  liquid  are  then  run  out  upon  another 
filter,  and  the  excess  of  liquid  caught  in  a  vessel  for  use  again. 
The  filters  containing  the  slag  and  cement  are  washed  with  ben- 
zine, dried  and  weighed  separately.  From  the  weights  the  per- 
centage of  adulteration  can  be  calculated.  The  slag  and  ce- 
ment can  then  be  analyzed  chemically,  if  thought  necessary,  as 
a  further  guide. 

Microscopic  Test. 

The  microscope  furnishes  us  with  a  very  good  means  of  detect- 
ing added  material  in  cement.  Butler1  recommends  that  those 
particles  which  pass  a  76  sieve  and  are  retained  upon  a  120  sieve 
be  examined  with  a  low  power  (say  one-inch)  objective.  The 
particles  of  pure,  well-burned  cement  clinker  of  this  size  will  then 
appear  dark,  almost  black  in  color,  resembling  coke  somewhat, 
and  will  possess  the  characteristic  spongy  honey-combed  appear- 
ance of  cement  clinker.  The  particles  of  less  well-burned  clinker, 
always  present  in  cement,  will,  when  examined  in  the  same  way, 
present  the  same  shape  and  structure,  but  will  differ  in  color, 
being  light  brown  and  semi-transparent,  resembling  gum  arabic. 
Intermediate  products  range  from  black  to  light  brown.  These 
particles  are  always  of  a  more  or  less  rounded  nature.  Particles 
of  slag  of  the  same  size  viewed  under  the  same  conditions  differ 
somewhat  in  color,  according  to  the  nature  of  the  slag.  Usually 
the  particles  are  light  colored,  of  angular  fracture,  and  instead  of 
the  particles  presenting  a  rounded  appearance  the  edges  are 
sharp  like  flint.  Not  to  be  mistaken  for  the  slag,  however,  are 
the  particles  of  pebbles  from  the  tube  mills  used  to  grind  the 
clinker.  These  latter  may  be  distinguished  from  the  slag  by  pick- 

1 "  Portland  Cement,"  p.  273. 


484  PORTLAND   CEMENT 

ing  out  the  particles  in  question  with  a  pair  of  pincers,  crushing 
them  in  a  small  agate  mortar  and  treating  them  with  hydrochloric 
acid.  The  slag  is  readily  attacked  while  the  debris  from  the 
pebbles  is  not  attacked.  Particles  of  iron  from  the  crushers  are 
also  present  in  the  residue  caught  upon  the  120  sieve.  These 
may  be  identified  by  their  black  metallic  appearance  and  their 
behavior  with  the  magnet.  Neither  of  these  can,  of  course,  be 
considered  as  adulterants.  Limestone  and  cement-rock  if  present 
are  in  more  or  less  flattened  particles,  and  the  latter  is  always 
dark  gray  in  color.  Both  of  these  may  be  readily  detected  by 
effervescence  with  dilute  acids.  The  foreign  particles  may  also 
be  picked  out  of  the  residue  with  a  pair  of  tweezers,  ground 
finely  and  identified  by  chemical  analysis. 


Chapter  XX. 


THE  INVESTIGATION  OF  MATERIALS  FOR  THE  MAN- 
UFACTURE  OF  PORTLAND  CEMENT. 


Prospecting  Limestone  and  Cement-Rock  Deposits. 

Properties  upon  which  it  is  intended  to  build  a  cement  plant 
should  be  very  carefully  prospected,  to  determine  not  only  the 
quality  but  also  the  quantity  of  the  materials  available.  The 
author  prefers  to  do  this  in  all  cases  by  drilling.  Many  geologists 
contend  there  are  properties  where  this  is  money  wasted.  When 
we  consider,  however,  that  the  building  of  a  modern  cement  plant 
entails  an  expenditure  of  seldom  less  than  $1,000,000  and  that 
a  thorough  drilling  of  a  property  can  usually  be  done  for  less  than 
$2,000,  it  would  seem  wisest  always  to  take  the  precaution  of 
doing  this.  The  author  has  met  with,  in  his  personal  experience, 
a  number  of  instances  where  expert  geologists  had  passed  upon 
properties  as  containing  inexhaustible  quantities  of  material  suit- 
able for  cement  manufacture,  which  after  being  drilled  were 
found  conclusively  to  contain  only  very  small  deposits.  In  one 
instance,  a  mill  was  built  and  it  was  found  on  opening  up  the 
limestone  beds  that  the  deposit  which  they  had  intended  to  use 
was  highly  magnesian  and  instead  of  having  to  go  only  a  few 
miles  for  this  material,  it  was  necessary  to  go  20  miles  away  from 
the  plant  before  suitable  low  magnesian  limestone  could  be  found. 
This  property  was  passed  upon  by  a  well  known  economic  geolo- 
gist. 

The  author  does  not  think  it  would  be  possible  to  form  any 
conclusion  as  to  cement-rock  without  drilling.  In  this  case,  sur- 
face samples  nearly  always  show  a  very  much  higher  percentage 
of  lime  than  is  contained  by  the  main  body  of  the  rock.  In  many 
places  throughout  the  Lehigh  belt,  the  cement-rock  is  overlaid  by 
a  thin  skin  of  limestone.  Five  per  cent,  of  carbonate  of  lime  will 
make  the  difference  between  an  economical  proposition  and  one 


486  PORTLAND 

which  is  not,  and  represents  usually  about  four  cents  per  barrel 
in  the  cost  of  manufacture.  A  very  accurate  estimate  should  be 
made  as  to  the  quality  of  the  rock  throughout  the  deposit  in  order 
that  the  quantity  of  limestone  required  to  bring  the  cement-rock 
up  to  the  proper  composition  for  the  manufacture  of  Portland 
cement  may  be  determined. 

The  prospecting  may  be  done  by  means  of  either  a  core  or 
churn  drill.  In  sinking  the  test  holes,  the  surface  dirt  and  clay 
should  be  shoveled  away  and  the  rock  exposed.  The  drill  can 
then  be  set  up  and  the  samples  taken.  The  hole  should  be  pro- 
tected from  surface  dirt,  etc.  by  placing  a  pipe  from  the  entrance 
of  the  hole  in  solid  rock  to  a  few  inches  above  the  ground. 

In  prospecting  a  property,  it  is  customary  to  make  a  map  show- 
ing the  topography,  etc.  and  this  should  be  divided  into  squares 
having  sides  of  say  50  to  300  ft.  according  to  the  uniformity  of 
the  material.  Drill  holes  can  then  be  sunk  at  the  corners  of  each 
square  and  the  cores  or  chips  brought  up  by  the  drill  saved  for 
analysis.  Usually  it  is  the  custom,  instead  of  making  one  sample 
of  all  of  the  rock  brought  up  from  a  hole,  to  make  several  samples 
of  the  material  brought  up  from  various  depths.  These  samples 
should  be  so  taken  that  every  inch  of  rock  through  which  the 
drill  passes  will  be  represented  in  the  sample.  Thus  one  sample 
should  represent  material  brought  up  from  a  depth  of  from  o  to 
5  feet,  while  the  next  should  represent  that  taken  by  the  drill  in 
going  from  5  to  10  feet,  etc.  By  doing  this,  the  uniformity  of 
the  deposit,  as  well  as  its  freedom  from  bands  of  magnesian 
stone,  etc.  can  be  tested.  After  the  analyses  are  all  made,  charts 
should  be  drawn  showing  the  quality  of  the  rock  at  various 
depths,  and  if  the  drilling  is  carried  far  enough,  the  depth  of  the 
deposit  at  each  point.  This  can  be  shown  easiest  by  means  of 
sections,  cutting  the  deposit  along  the  line  of  squares,  drawn  to 
scale  and  showing  by  means  of  various  kinds  of  shading  the 
stripping,  etc.  From  these  charts  the  amount  of  rock  available 
and  the  dirt  which  must  be  removed  to  get  at  this  can  be  calcu- 
lated. Such  a  chart  is  shown  in  Fig.  164. 

In  sampling  with  the  churn  drill  the  chips  or  mud  from  this 


THE  INVESTIGATION   OF   MATERIALS 


487 


should  be  dumped  into  a  large  tub  and  when  all  of  these  from  a 
given  portion  of  the  hole  have  been  placed  in  this  the  mud  should 
be  stirred  up  well  and  an  average  sample  of  this  taken.  This 
mud  sample  may  be  placed  in  a  shallow  tin  pan  and  dried  on  the 
boiler  of  the  drill,  after  which  it  should  be  sent  to  the  laboratory 
in  clean  bags  of  cloth  or  paper  or  in  tin  boxes.  In  the  laboratory, 
the  sample  should  be  ground  and  quartered  down  to  laboratory 
dimensions  and  the  final  sample  made  to  pass  a  No.  100  mesh 


sieve. 


Core  drillings  are  also  much  used  in  prospecting  limestone. 
These  cut  a  round  cylinder  or  core  of  rock  from  one  to  two  inches 


Fig.  164.— Cross-section  showing  limestone  deposit. 

in  diameter,  as  they  pass  into  the  rock.  They  may  be  obtained 
run  by  either  steam,  gasoline  or  electricity.  For  some  purposes 
these  cores  are  very  valuable  as  they  allow  a  minute  inspection  of 
the  beds  as  to  stratification,  etc.  and  any  thin  bands  of  foreign 
material,  such  as  quartz  are  shown.  The  machines  themselves, 
however,  are  expensive  and  troublesome  to  operate  as  the  cutting 
is  usually  done  by  diamonds  set  in  the  ends  of  the  drill.  Recent- 
ly a  number  of  core  drills  have  been  brought  out  which  use  a 
steel  cutting  edge.  These,  however,  are  less  efficient  than  the 
diamond  drill  and  generally  speaking,  in  spite  cf  lower  first 
cost,  are  no  more  economical  in  the  long  run  than  the  diamond 
drill. 

In  some  instances  less  drilling  would  have  to  be  done  by  a 
core  drill  than  by  a  churn  drill,  as  the  churn  drill  can  only  be 
used  to  sink  a  vertical  hole  while  the  core  drill  can  be  used  for 
one  at  any  angle.  For  instance,  by  referring  to  Fig.  165  which  is  a 


488  PORTLAND 

section  across  a  limestone  deposit  with  a  strike  of  about  45°,  it  will 
be  seen  that  if  we  prospect  with  a  churn  drill,  we  would  have  to 
drill  in  the  direction  shown  by  the  line  AC,  or  across  the  beds  at 
an  angle,  while  if  we  used  a  core  drill  the  drilling  could  be  done 
along  the  line  AE,  or  perpendicular  to  the  beds,  which  would 
give  us  a  sample  of  exactly  the  same  beds  as  along  the  line  AC. 
In  this  case  the  churn  drill  would  give  us  just  as  good  a  sample 
as  the  core  drill  but  the  amount  of  drilling  required  to  penetrate 
all  the  beds,  as  will  be  seen,  is  much  greater.  In  the  case  of  a 
limestone  deposit  with  a  practically  vertical  pitch,  the  only  meth- 
od of  drilling  which  can  be  employed  to  advantage  is  a  core  drill, 
as  this  can  be  used  to  sink  holes  at  right  angles  to  the  strike  of 


C 

Fig.  165.—  limestone  strata  pitched  at  an  angle. 

the  deposit,  while  the  churn  drill  would  penetrate  only  a  few  beds. 

Some  authorities  contend  that  in  sampling  limestone  pitched 
at  an  angle  such  as  that  shown  in  Fig.  165,  it  would  be  unnecessary 
to  drill  and  all  that  is  necessary  would  be  to  take  surface  sam- 
ples along  the  line  AD.  It  is  highly  probable  that  where  the 
limestone  beds  are  exposed  either  as  shown  in  this  illustration  or 
Fig.  1 66  that  very  accurate  conclusions  as  to  both  the  quality  and 
the  quantity  of  the  deposit  can  be  formed  by  sampling  along  the 
lines  AD.  Where  conclusions  have  to  be  drawn,  however,  upon 
data  of  this  sort,  the  services  of  an  expert  should  always  be 
employed,  as  considerable  experience  is  necessary  in  order  that 
false  and  misleading  conclusions  may  not  be  drawn. 

In  calculating  the  quantity  of  material  available  it  is  sufficient- 
ly accurate  for  ordinary  purposes  to  assume  that  one  ton  of 


THE  INVESTIGATION  OF   MATERIALS  489 

material  as  quarried  will  produce  3.3  barrels  of  cement  If  the 
mixture  is  four-fifths  limestone  and  one-fifth  shale,  then  four- 
fifths  ton  of  limestone  will  produce  3.3  barrels,  or  one  ton  of 
limestone  will  produce  4.1  barrels  of  cement  and  one  ton  of 
shale  will  produce  i6l/2  barrels  of  cement.  For  practical  pur- 
poses it  may  also  be  assumed  that  one  cubic  foot  of  limestone  will 
weigh  160  pounds  and  that  a  cubic  foot  of  shale  will  weigh  125 
pounds.  The  actual  weights  may  be  determined  by  taking  the 
specific  gravity  of  the  stone  and  multiplying  this  by  62.4,  which 
will  give  the  weight  in  pounds  of  a  cubic  foot  of  solid  material. 


Fig.  166.—  limestone  strata  exposed  by  a  ravine. 

Roughly  speaking,  each  acre  of  limestone  will  produce  14,290 
barrels  of  cement  for  each  foot  in  depth  and  one  acre  of  shale 
will  produce  57,500  barrels  of  cement  for  each  foot  in  d^pth, 
when  the  proportions  between  the  two  are  5  to  I.  That  is,  a 
property  ten  acres  in  area  with  a  limestone  deposit  100  feet  deep 
will  produce  14,290,000  barrels  of  cement  when  the  limestone 
is  mixed  with  one-fifth  its  weight  of  shale.  Referring  again  to 
Fig.  166  which  illustrates  the  cross-section  of  a  limestone  deposit 
pitched  at  an  angle,  it  may  be  noted  that  in  calculating  the 
quantity  of  limestone  available,  it  is  not  correct  to  consider  the 
parallelogram  ABCD  as  a  cross-section  of  this.  The  cross-sec- 
tion of  the  available '  stone  is  represented  by  the  triangle  ACD, 
since  manifestly  it  would  not  be  possible  by  open  quarrying  meth- 
ods to  get  out  the  rock  lying  in  the  wedge  ABC,  when  overlaid 
by  such  loose  material  as  shale. 

Clay  and  Shale. 
Clay  can  be  sampled  in  a  number  of  ways,  such  as  by  digging 


490  PORTLAND    CEMENT 

pits  or  sinking  test  holes  by  jneans  of  a  soil  sampler,  auger  drill 
or  a  serrated  pipe.  Hard  clays  and  shales  will  require  either 
the  auger,  diamond  or  churn  drill.  The  auger  drill,  for  use  in 
sampling,  is  similar  to  those  used  for  coal  cutting,  etc.  The 
serrated  pipe  consists  of  a  pipe,  the  end  of  which  has  been  filed 
and  tempered  to  form  sharp  teeth  like  a  saw.  This  is  forced 
down  into  the  clay  by  twisting  a  handle  at  the  upper  end.  The 
result,  when  withdrawn,  is  a  plug  of  clay,  filling  the  pipe  and 
representing  the  strata  through  which  the  latter  has  passed. 
The  soil  sampler  consists  of  a  short  auger  6  inches  long  and 
about  4  inches  in  diameter  mounted  on  a  long  jointed  iron  rod 
provided  with  a  wooden  handle  at  its  upper  end.  It  may  be 
purchased  of  houses  dealing  in  laboratory  supplies.  It  is  used 
similar  to  the  pipe  and  a  plug  of  clay  is  obtained  on  the  auger. 
The  rod  is  usually  jointed  in  lengths  of  a  yard. 

Clay  deposits  should  be  mapped  out  carefully,  as  different  parts 
of  the  bed  may  show  very  different  proportions  of  silica  and 
alumina,  and  in  order  to  get  a  cement  with  uniform  setting  prop- 
erties it  may  be  necessary  to  work  two  or  more  parts  of  the  de- 
posit in  conjunction,  to  keep  the  ratio  between  tne  silica  and 
alumina  constant. 

The  depth  of  the  deposit  should  also  be  determined  so  that  a 
calculation  of  the  available  quantity  of  clay  may  be  made. 

Marl. 

For  sampling  marl,  a  tube,  similar  to  that  used  for  sampling 
cement,  may  be  employed  to  advantage.  This  is  described  on 
page  355,  or  the  serrated  pipe  described  before  may  be  used.  If 
the  marl  deposit  is  very  wet,  a  long  pipe  having  a  plug  at  one  end 
may  be  used.  This  plug  should  be  of  iron,  have  a  sharp  point,  fit 
the  mouth  of  the  pipe  closely  and  be  fastened  to  a  long  thin  iron 
rod.  In  using  the  sampler,  the  iron  plug  is  drawn  up  against  the 
mouth  of  the  pipe  and  the  latter  is  thus  shoved  down  to  the  depth 
at  which  the  sample  is  to  be  taken.  The  pipe  is  then  raised  and 
shoved  down  to  its  former  level,  being  forced  tight  against  the 
iron  plug.  The  pipe  is  then  raised  by  means  of  the  rod  and  the 
sample  dumped  out. 


THE  INVESTIGATION  OF   MATERIALS  491 

If  the  marl  is  fairly  dry  the  soil  sampler  described  above  may 

be  used. 

Marl  deposits  should  be  very  thoroughly  mapped  out,  not  only 
as  to  quality  but  also  as  to  the  depth  of  the  deposit  in  order  that 
the  quantity  available  for  manufacturing  purposes  may  be  calcu- 
lated, since  the  value  of  marl  deposits  depends  in  most  cases  as 
much  upon  quantity  as  quality. 

TRIAL  BURNINGS. 

In  prospecting  new  deposits  of  raw  materials,  it  is  often 
thought  advisable  to  make  up  small  trial  lots  of  cement  in  the 
laboratory  and  examine  into  the  physical  properties  of  these.  For 
such  trials,  it  is  necessary  to  crush  the  raw  materials,  if  they  are 
not  already  in  small  pieces,  and  correctly  proportion  them.  The 
mixture  is  then  finely  ground,  the  powder  moistened  with  water 
and  moulded  into  little  cubes  or  balls  and  these  latter  are  burned 
in  some  form  of  laboratory  kiln.  The  resulting  clinker  is  then 
sorted  to  separate  out  the  under-burned,  and  the  hard-burned 
portions  are  ground  to  the  same  degree  of  fineness  as  commercial 
cement.  It  is  also  often  desirable  to  make  experimental  burnings 
in  the  investigation  of  the  various  problems  which  arise  in  con- 
nection with  the  manufacture  and  properties  of  cement.  The 
apparatus  described  below  is  suitable  for  such  purposes  and  has 
been  used  in  similar  work  by  various  investigators. 

For  crushing  the  raw  rock  small  Blake  or  Bosworth  crushers 
such  as  are  used  in  almost  all  laboratories  for  crushing  ores  will 
be  found  convenient.  These  can  be  so  adjusted  as  to  crush  the 
rock  to  about  wheat  size  and  finer.  They  can  be  obtained  either 
hand  or  power  driven,  but  for  the  work  indicated  above  they 
should  be  power  driven  and  attached  to  a  shafting  somewhere 
about  the  mill  or  run  by  an  independent  motor.  After  crushing 
the  materials  to  the  size  indicated  above  they  should  be  carefully 
analyzed  and  mixed  in  the  proper  proportions  (see  Chapter  IV). 
The  mixture  should  then  be  finely  ground.  The  degree  of  fine- 
ness should  be  indicated  by  the  nature  of  the  investigation.  If  a 
test  is  being  made  of  the  suitability  of  certain  raw  materials  the 


492 


PORTLAND   CEMENT 


mixture  should  be  ground  no  finer  than  it  would  be  in  actual  mill 
practice,  or  about  95  per  cent,  through  a  100  mesh  sieve. 

Samples  of  clay  and  marl  should  be  thoroughly  dried  before 
analyzing  and  proportioning  them.  This  can  be  done  over  a  hot 
plate  or  steam  radiator,  etc. 

For  finely  grinding  the  mixture,  a  jar  mill  will  be  found  as 
convenient  as  anything  else.  Fig.  167  shows  the  form  (made  by 
the  Abbe  Engineering  Co.)  which  the  writer  has  used  in  his 
laboratory  and  found  very  satisfactory.  This  consists  of  a  porce- 


COPYRIGHTjLl904,   BY  ABBfe  ENGINEERING  Co. 

Fig.  167.— Jar  mill. 

lain  jar,  the  cover  of  which  is  fastened  tightly  on  by  means  of  a 
clamp,  as  shown.  The  jar  itself  is  held  in  a  revolving  frame  by 
brass  bands,  one  of  which  can  be  loosened  by  means  of  a  thumb 
screw,  allowing  the  jar  to  be  removed  from  the  frame.  The  jar 
is  filled  half  full  of  porcelain  balls  and  as  the  former  revolves  the 
material  is  ground  by  the  latter.  The  jar  is  intended  to  make 
from  40  to  50  revolutions  per  minute  and  will  grind  about  15 
pounds  of  material  at  a  charge. 

After  grinding  finely,  the  powder  is  mixed  with  water  until  it 
is  plastic  and  then  moulded  into  small  cubes  or  balls.  The  writer 
has  usually  found  it  an  excellent  plan  to  roll  the  mass  out  in  a 


THE  INVESTIGATION   OF   MATERIALS 


493 


thin  sheet  on  a  pane  of  glass  or  an  oiled  board  and  then  cut  this 
into  blocks  with  the  point  of  a  spatula  or  trowel.  The  size 
of  the  balls  or  cubes  will  depend  upon  the  size  of  the  furnace — a 
small  furnace  will  require  a  smaller  ball  than  a  larger  one.  They 
should  not,  however,  be  smaller  than  a  pea  for  even  a  small  fur- 
nace. 

For  burning  small  quantities  of  cement  the  writer  has  found 


Fig.  168. — Furnace  for  experimental  burnings. 

the  form  of  kiln  shown  in  Fig.  168  useful.  It  consists  of  a  large 
Battersea  crucible  (size  R)  13  inches  in  height  and  10  inches  in 
diameter,  resting  on  a  piece  of  fire-brick,  C,  and  fitting  snugly  in- 
to a  cylinder  of  concrete,  B.  The  crucible  is  punched  with  four 
holes  F,  F,  F,  F,  around  its  bottom  and  through  these  the  air 


494  PORTLAND    CEMENT 

for  combustion  enters  the  crucible.  A  tight  joint  between  the 
crucible  and  the  concrete  cylinder  is  made  by  means  of  fire-clay 
or  wet  asbestos  as  shown  at  E,  E.  Air  is  brough*  into  the  con- 
crete cylinder  by  means  of  the  pipe  D.  F,  F,  is  a  sheet  iron 
jacket  surrounding  the  cylinder  of  concrete.  The  walls  of  the 
cylinder  are  about  6  inches  thick.  Air  for  burning  may  be 
obtained  from  a  compressor  or  a  small  Root  or  Crowell  blower. 
Larger  crucibles  than  the  size  indicated  can  be  obtained  when  a 
larger  furnace  is  needed.  The  one  given  above  will  burn  3  or 
4  pounds  of  cement.  Charcoal  or  oil  coke  is  used  as  a  fuel.  A 
small  piece  of  cotton  waste  saturated  with  oil  is  placed  in  the 
crucible  and  when  this  is  burning  a  few  handfuls  of  charcoal 
are  added  and  the  air  blast  turned  on.  As  soon  as  the  charcoal  is 
burned  and  the  crucible  is  heated  up,  it  is  filled  half  full  of  char- 
coal and  the  little  balls  of  slurry  are  added  in  a  thin  layer.  More 
charcoal  is  placed  over  this  and  then  more  slurry,  etc.,  until  the 
crucible  is  full.  A  pair  of  fire-bricks  having  an  inch  channel  cut 
in  one  side  of  each  is  then  placed  over  the  crucible  to  form  a 
cover  and  the  heating  continued  until  all  the  charcoal  is  burned 
away.  The  air  is  left  turned  on  to  cool  the  clinker  after  which 
the  latter  is  sorted. 

Another  form  of  furnace  which  the  writer  has  used  in  his 
laboratory  of  recent  years  is  shown  in  Fig.  169.  This  consists 
of  a  small  cylinder  of  boiler  iron  a  (which  by  the  way  was  part 
of  an  old  stack)  lined  with  fire-brick.  This  is  provided  with  an 
iron  plate,  b,  perforated  with  holes  as  shown.  The  opening  c 
below  the  grate  is  closed  by  means  of  a  cast-iron  door  and  the 
cracks  around  this  are  plastered  tight  with  clay,  or  better  still 
wet  asbestos  paper,  which  can  be  rammed  into  the  cracks  very 
tightly.  Air  is  blown  in  at  d  by  means  of  a  fan  or  pressure 
blower.  In  using  the  furnace,  a  little  broken  fire-brick,  in  pieces 
about  an  inch  in  size,  is  placed  on  the  wrought  iron  plate  to 
prevent  this  being  damaged  by  the  heat.  Fire  is  kindled  upon 
this,  charcoal  being  used  as  fuel,  the  burning  being  conducted 
just  as  described  above.  When  the  burning  is  completed,  the 
iron  plate  is  tilted  so  as  to  allow  the  clinker  and  ashes  to  drop 


THE;  INVESTIGATION  OF  MATERIALS 


495 


into  the  pit  beneath.     From  this   it  is  drawn  out  through  the 
opening  c  by  means  of  a  small  scraper,  sorted  and  ground. 

For  research  work  when  contamination  with  the  fuel  ash  is 
objectionable,  a  small  Fletcher  furnace  lined  with  a  mixture  of  90 


Fig.  169. — Shaft  kiln  for  trial  burnings. 

parts  coarse,  burned  magnesite  and  10  parts  Portland  cement  will 
be  found  useful. 

Bleininger  describes1  a  kiln  used  in  the  Ohio  State  University 
Ceramic  Department.  This  consists  of  a  straight  shaft  of  fire- 
brick with  walls  4  inches  thick,  divided  into  three  distinct 
divisions.  Air  is  forced  into  a  space  4  inches  high  at  the  bottom 
under  a  pressure  of  about  12  ounces  from  a  blower  through 
a  2-inch  pipe.  This  space  is  divided  from  the  next  division  by 
means  of  a  cast-iron  plate  provided  with  concentric  rows  of  holes. 
Above  this  plate  about  5  inches  away  from  it  an  iron  pan  is 
supported  by  two  bricks.  Petroleum  is  fed  into  thi§  pan  by 
means  of  a  }4-inch  pipe,  running  in  by  gravity  from  a  can  some 
distance  away.  Several  inches  above  the  pan  the  whole  cross- 

1  Ohio  Geol.  Survey,  Bui.  No.  3  [IV]  Manufacture  of  Hydraulic  Cements. 


496  PORTLAND    CEMENT 

section  of  the  shaft  is  filled  with  broken  fire-brick.  Above  this 
compartment  the  third  compartment  is  formed  by  a  grating  of 
bricks,  made  of  a  mixture  of  80  per  cent,  magnesite  and  20  per 
cent.  Portland  cement.  On  this  grating  the  balls  of  cement  mix- 
ture are  heaped  up  to  the  top  of  the  compartment,  which  is  about 
8  inches  high.  The  cover  consists  of  a  perforated  clay  tile  upon 
which  are  piled  broken  bricks.  The  clinker  compartment  is 
accessible  from  the  outside  by  means  of  a  door  which  is  closed  by 
a  fire-brick  plug  which  can  be  removed  and  the  clinkers  with- 
drawn and  examined. 

To  start  the  furnace,  a  small  amount  of  paper  and  wood  is 
placed  upon  the  pan  through  a  hole  provided  for  this  purpose. 
The  oil  on  coming  in  contact  with  the  hot  pan  is  vaporized  and 
mixes  with  the  air  in  the  compartment  filled  with  broken  brick. 
The  time  required  for  a  burn  in  this  kiln  is  about  two  hours.  By 
removing  the  pan,  bricks  and  broken  pieces  of  brick  this  kiln  can 
also  be  used  for  burning  with  coke. 

When  large  quantities  of  cement  are  to  be  burned  a  small  shaft 
kiln  made  of  fire-brick  and  provided  with  grate  bars  can  be  used. 
The  cement  mixture  and  coke  being  charged  in  alternate  layers 
after  the  furnace  is  well  heated  up  and  a  bed  of  hot  coals  is  ob- 
tained on  the  grate  bars.  The  temperature  of  such  a  kiln  can  be 
greatly  increased  by  providing  means  of  blowing  air  through  the 
grate  bars. 

Prof.  E.  D.  Campbell,  of  the  University  of  Michigan,  used  in 
his  experimental  work  a  small  rotary  kiln  consisting  of  an  iron 
pipe,  8  inches  in  diameter  and  32  inches  long.  This  was  lined 
with  four  sections  of  hard-burned  magnesite  pipe,  3  inches  in- 
ternal diameter,  and  was  revolved  by  means  of  a  ^-horse-power 
motor,  at  a  speed  of  one  revolution  in  85  seconds.  It  was  fired 
by  means  of  a  Hoskins  gasoline  burner  under  an  air  pressure  of 
50  pounds. 

After  sorting  the  clinker  it  is  crushed  and  ground  in  the  jar 
mill  mentioned  before,  the  degree  of  fineness  being  regulated  by 
conditions.  Plaster  or  gypsum  must,  of  course,  be  added  to  slow 
the  set  of  the  resulting  cement  and  may  be  ground  in  with  the 
clinker. 


APPENDIX. 


Tables. 

TABLE  XLIX. — THE  ATOMIC  WEIGHTS  OF  THE  MORE  IMPORTANT 
ELEMENTS.    O  =  16. 


Name 

Symbol 

Weight 

Name 

Symbol 

Weight 

Al 
Sb 
As 
Ba 
Bi 
B 
Br 
Cd 
Ca 
C 
Cl 
Ch 
Co 
Cu 
F 
Au 
H 
I 

27.1 
120.2 
74.96 
137.37 
2oS.O 
11.0 
79.92 
112.40 
40.09 
12.  OO 
35.46 
52-0 
58.97 
63.57 
19.O 
197.2 
1.008 
126.92 

Fe 
Pb 
Mg 
Mil 
Hg 
Ni 
N 
0 
P 
Pt 
K 
Si 
Ag 
Na 
Sr 
S 
Sn 
Zn 

55.85 
207.10 
24.32 
54-93 

200.00 
58.68 
14.01 

1  6.00 
31.00 
195-00 
39.10 
28.03 
107.88 
23.00 
87.62 
32.07 
119.00 
65-37 

Lead  

N  irk  el 

Carbon  

Silicon  •  

Pnh»U 

qiiver 

Gold  

Tin  

TABLE  U— FACTORS. 


Found 

Sought 

Factor 

Found 

Sought 

Factor 

Lime 

Pa(  > 

PaPO 

I    iRAAl 

Sulphur 
BaSO    

s 

O  I^7l8 

PaPO 

PaO 

BaSQ    

SO, 

O  ^4^OO 

Pa  SO 

PaO 

OA.  I  I  Q^ 

BaSO    

CaSO4 

O  StM27 

PaSO 

PaPO 

RaSO 

(CaSO  )  H  O 

w'O"O-e/ 

o  62  184 

PnS 

PaO 

./oouo 

RaSO 

CaSO  2H  O 

O  TV  *»6 

paq 

PaSO 

u.  //y  10 
I   <S872O 

BaSO    «  «  « 

CaS 

^'  /^'O" 
O  "^OQOQ 

PO 

PaPO 

2  27472 

Raj^O    

H  SO 

o  42016 

*-U2     

MuO 

PaO 

^'z/4/-' 

QdS    

•"2°  ^4 

S 

O  22  IQ'* 

JMgW    • 

i.^ycuju 

PrlS 

CaS 

o  4082^ 

Magnesia 

Mir  P  (  ) 

MgO 

Ol62IQ 

Alkalies 
K  PtCl  

K>O 

o  10^84. 

1Y1&21  2^7       ' 
TVTcr   P  O 

MtrPO 

KPtPl 

KC1 

o  30686 

•Mgyf  2U7    '  ' 
\\  crO 

iugv_v^3 
Mp-po 

u./O/44 

NaPl   . 

Na  O 

o  53028 

MgU   
PaO  .  . 

KN-v-'3 

MffO 

O  7  1  Qd.^ 

MgC03  -  •  • 

CJ-W 

MgO 

"VTrr("*O 

0.47X18 

Miscellaneous 
AgCl  

HC1 

0.25442 

°2     

1.91636 

QO      

c 

O  2727^ 

Iron 

"FV 

Fe  O 

I  A.2Q7  I 

Mg2P207  

P205 

0.63780 

Fe 

Flo 

I   28650 

Fe203  
Fe203  

Fe 
FeO 

0.69943 
0.89983 

32 


498 


PORTLAND 


TABLE  LI.— FOR  CONVERTING  Mg2P2O7  TO  MgO. 


Percentage 
of  MgO 
0.5  gram 
sample 

Grams  of  MgaPgO;  weighed 

.00 

.OI 

.02 

.03 

.04 

•05 

.06 

.07 

.08 

.09 

.0138 
•0152 
.0166 
.0180 
.0193 
.0207 
.0221 
•0235 
.0249 
.0262 
.0276 
.0290 
.0304 
.0318 
•0331 
•0345 
•0359 
•0373 
.0387 
.0400 
.0414 
.0428 
.0442 
.0456 
.0470 
.0483 

•0139 
•0153 
.0167 
.Ol8l 

•0195 
.O2O9 
.0222 
.0236 
.0250 
.0264 
.0278 
.0291 
.0305 
.0319 
•0333 
•0347 
.0360 

•0374 
.0388 
.O4O2 
.0416 
.0429 

.0443 
•0457 
.0471 
.0485 

.OF4I 

.0155 
.0168 
.0182 

.0196 
.0210 
.0224 

.0238 
.0251 
.0265 
.0279 
.0293 
.0307 
.0320 

•°334 
.0348 
.0362 
.0376 
.0389 
.0403 
.0417 
.0431 

.0445 
.0458 
.0472 
.0486 

.0142 
.0156 
.0170 
.0184 
.0197 

.0211 
.0225 
•0239 
.0253 
.0267 
.0280 
.0294 
.0308 
.0322 
.0336 
.0349 
•0363 
.0377 
.0391 
.0405 
.0419 
.0432 
.0446 
.0460 
.0474 
.0488 

.0144 
.0158 
.OI7I 
.0185 
.0199 
.0213 
.0226 
.0240 
.0254 
.0268 
.0282 
.0296 
.0309 
.0323 
.0337 
.0351 
.0365 
.0378 
.0392 
.0406 
.O42O 

•0434 
.0447 
.0461 

•0475 
.0489 

.0145 

•0159 
.0173 
.0186 
.O2OO 
.0214 
.0228 
.0242 
.0255 
.0269 
.0283 
.0297 
.0311 
•0325 
•0338 
.0352 
.0366 
.0380 

•0394 
.0407 
.O42I 

.0435 
.0449 
.0463 
.0477 
.0490 

.0146 
.Ol6o 
.0174 
.0188 
.0202 
.0215 
.0229 
.0243 
.0257 
.0271 
.0285 
.0298 
.0312 
.0326 
.0340 

•0354 
.0367 
.0381 

•0395 
.0409 
.0423 
.0436 
.0450 
.0464 
.0478 
.0492 

.0148 
.Ol62 
.0175 
.0189 
.0203 
.C2I7 
.0231 
.0244 
.0258 
.0272 
.0286 
.0300 
.0314 
.0328 
.0341 

.0355 
.0369 

.0383 
.0396 
.O4IO 
.0424 
.0438 
.0452 
.0465 
.0479 
•0493 

.0149 
.0162 
.0177 
.OI9I 
.O2O4 
.0218 
.0232 
.0246 
.0260 
.0273 
.0287 
.0301 

.0315 
.0329 

.0343 
.0356 
.0370 
.0384 
.0398 
.O4I2 
.0425 
•0439 
•0453 
.0467 
.0481 
-0495 

.0151 
.0164 
.0178 
.0192 
.O2O6 
.O22O 
•0233 
.0247 
.026l 
.0275 
.0289 
.0302 
.0316 
.0330 
.0344 
.0358 
.0372 

.0385 
•0399 
.0413 
.0427 
.0441 

•0454 
.0468 
.0482 
.0497 

jo 

20  • 

10  . 

•y  •  • 
/to  . 

CQ  .  . 

60  

7O  •  • 

80  

QO  •  . 

2  OO  

2  JO  

2  2O  

2  1C\ 

^•ou  • 

••v  

2  ^O 

•*ou  

2  ^O  • 

2io.:::: 
2.90  
3-ro  

3-io  

3-20  

3-30  
3-40  
3-50  

TABLE  LIT.— FOR  CALCULATING  THE  PERCENTAGE  OF  LIME  OR  CAR. 

BONATE  OF   LlME  WITH  ONE-HALF  GRAM  SAMPLE.1 


55-o  cc. 

55-i  cc. 

55-2  cc. 

CaO 

CaCO8 

CaO 

CaC03 

CaO 

CaCO3 

I   I.OlS 

1.816 

I    I.OI6 

1.814 

I    I.OI5 

1.812 

2  2.036 

3.632 

2   2.032 

3.628 

2    2.O3O 

3.624 

3  3-054 

5-448 

3  3-048 

5.442 

3  3-°45 

5.436 

4  4-072 

7.264 

4  4.064 

7.256 

4  4.060 

7.248 

5  5-090 

9.080 

5  5-080 

9.070 

5  5.075 

9.060 

6  6.108 

10.896 

6  6.096 

10.884 

6  6.090 

10.872 

7  7.126 

12.712 

7  7.112 

12.698 

7  7-105 

12.684 

8  8.144 

14.528 

8  8.128 

14.512 

8  8.120 

14.496 

9  9.162 

16.344 

9  9-144 

16.326 

9  9.135 

16.308 

1  Chemical  Engineer ,  i.,  42. 


TABLES 


499 


TABLE  LIL— (Continued] 


55-3  cc. 

55-4  cc. 

55-5  cc. 

CaO 

CaCOa 

CaO 

CaCO3 

CaO 

CaCO3 

I    1.013 

1.  808 

I    I.  Oil 

1.805 

I    1.009 

1.801 

2   2.026 

3.616 

2    2.022 

3.610 

2   2.0l8 

3.602 

3  3-°39 

5424 

3  3.033 

5.415 

3  3.027 

5.403 

4  4.052 

7.232 

4  4.044 

7.22O 

4  4.036 

7.204 

5  5-065 

9.040 

5   5-055 

9.025 

5  5045 

9.005 

6  6.078 

10.848 

6  6.066 

10.830 

6  6.054 

10.806 

7  7-09  r 

12.656 

7  7.077 

12.635 

7  7-063 

12.607 

8  8.104 

14.464 

8  8.088           14.440 

8  8.072 

14.408 

9  9-II7 

16.262 

9  9-099 

16.245 

9  9.081 

16.209 

55  6  cc. 

55-7  cc. 

55-8  cc. 

CaO 

CaCO3 

CaO 

CaCO4 

CaO 

CaC03 

I    1.007 

1-797 

I    1.005 

1-794 

I    1.004 

1.792 

2   2.014 

3-594 

2    2.010 

3-588 

2   2.OO8 

3.584 

3  3.021 

5-391 

3  3.oi5 

5.382 

3   3°'2 

5.376 

4  4.028 

7.188 

4  4.020 

7.176 

4  4  oio 

7.168 

5  5-035 

8.985 

5  5.025 

8.970 

5  5-020 

8.960 

6  6.042 

10.782 

6  6.030 

10.764 

6  6.024 

10.752 

7  7-049 

12.579 

7  7.035 

12.558 

7  7.028 

12.544 

8  8.056 

14-376 

8  8.040 

H.352 

8  8.032 

14.336 

'  9  9.063 

16.173 

9  9-045 

16.146 

9  9.036 

16.128 

55-9  cc. 

56.0  cc. 

56.1  cc. 

CaO 

CaCO3 

CaO 

CaCO8 

CaO 

CaCO3 

I    I.OO2 

1.789 

I    I.OOO 

1.785 

I   0.998 

1.782 

2   2.004 

3.578 

2   2.800 

3-570 

2    1.996 

3.564 

3  3.oo6 

5.367 

3  3-000 

5-355 

3  2.995 

5.346 

4  4.008 

7.I56 

4  4.000 

7.140 

4  3-993 

7.128 

5  5-010 

8-945 

5  5-000 

8.925 

5  4.991 

8.910 

6  6.012 

10.734 

6  6.000 

10.710 

6  5-989 

10.692 

7  7.oi4 

12.523 

7  7.000 

12.495 

7  6.987 

12.474 

8  8.016 

14.312 

8  8.000 

14.280 

8  7.986 

14.256 

9  9.018 

ib.ioi 

9  9.000 

16.065 

9  8.984 

16.038 

56.2  cc. 

56.3  cc. 

56.4  cc. 

CaO 

CaC03 

CaO 

CaC03 

CaO 

CaCO3 

I   0.996 

1.779 

I   0.995 

1.776 

I  0.993 

1.773 

2    1.992 

3.558 

2    1.990 

3.552 

2    1.986 

3-546 

3  2.9*8 

5-337 

3  2.985 

5.328 

3  2.979 

5  3r9 

4  3-984 

7.116 

4  3.980 

7.104 

4  3-972 

7.092 

5  4-980 
6  5.976 

8.895 
10,674 

5  4-975 
6  5-970 

8.880 
10.656 

5  4.965 
6  5.958 

8.86*5 
10.638 

7  6.972 

13-453 

7  6.965 

12.432 

7  6.951 

12.411 

8  7.968 

14.232 

87.960 

14.408 

8  7.944 

14.184 

9  8.964 

16.011 

9  8.955 

15.984 

9  8.937 

15-957 

5oo 


PORTLAND    CEMENT 
TABLE  LIT.— (Continued] 


56.5  cc. 

56.6  cc. 

56.7  cc. 

CaO 

CaC03 

CaO 

CaC03 

CaO 

CaC03 

I  0.991 

1.770 

I  0.989 

1.767 

I  0.988 

1.764 

2    1.982 

3-540 

2    1.978 

3-534 

2    1.976 

3.528 

3  2973 

5-310 

3  2.967 

5-301 

3  2.964 

5.292 

4  3  964 

7.080 

4  3.956 

7.068 

4  3-952 

7.056 

5  4-955 

.    8.850 

5  4-945 

8.«35 

5  4-940 

8.820 

6  5.946 

10.620 

6  5-934 

10.602 

6  5-928 

10.584 

7  6.937 

12.390 

7  0.923 

12.369 

7  6.916 

12.348 

8  7.928 

14.  160 

8  7.912 

14.136 

8  7.904 

14.112 

9  8.919 

15-930 

9  8.901 

15-9^3 

9  8.892 

15.876 

56.8  cc. 

56.9  cc. 

57.0  cc. 

CaO 

CaC03 

CaO 

CaC03 

CaO 

CaC08 

I  0.986 

1.761 

I  0.984 

1-757 

I  0.983 

1-754 

2    1.972 

3-522 

2    1.968 

3-5I4 

2    1.966 

3.508 

3  2.958 

5-283 

3  2.952 

5-271 

3  2.949 

5.262 

4  3-944 

7.044 

4  3  «36 

7.028 

4  3-932 

7.016 

5  4.930 

8,805 

5  4.920 

8.785 

5  4.9I5 

8.770 

6  5.916 

10.566 

6  5.904 

10.542 

6  5-898 

10.524 

7  6.902 

12.327 

7  6888 

12.2    9 

7  6.881 

12.278 

8  7.888 

14.088 

8  7-872 

14.056 

8  7.864 

14.032 

9  8.874 

15.849 

9  8.856 

15.813 

9  8.847 

15.786 

The  first  column  of  each  table  gives  the  number  of  cubic 
centimeters  of  permanganate  required  by  0.5  gram  of  calcite  (see 
page  267),  and  the  second  and  third  columns  show  the  corres- 
ponding percentages  of  calcium  oxide  and  calcium  carbonate 
respectively  where  a  half  gram  sample  has  been  taken. 

Example  of  the  use  of  tables. — Suppose  0.5  gram  of  calcite 
takes  55.6  cc.  of  permanganate,  then  write  the  values  found  in 
the  table  headed  55.6  cc.  on  a  card  and  stand  near  the  burette 
table.  The  writer  usually  notes  the  CaO  values  in  red  ink  and 
the  CaCO3  in  black  to  avoid  confusing  them. 

Now  suppose  we  analyze  a  limestone  and  find  it  requires  51.3 
cc.  then  the  percentage  of  lime  and  carbonate  of  lime  may  be 
calculated  from  the  table  as  follows : 


50.0 

I.O 

3 


cc. 
cc. 

cc. 


CaO 
50.35 
1.007 


5I.6591 


CaC03 
89-85 

1.797 
.5391 
92.1861 


TABLES 


501 


LIII. — PERCENTAGES  OF  WATER  FOR  SAND  MIXTURES. 


Neat. 

i-i 

1-2 

1-3 

-5 

18 

12.0 

10.0 

9.0 

8.4 

8.0 

19 

12-3 

10.2 

9-2 

8-5 

8.1 

20 

12.7 

10.4 

93 

87 

8.2 

21 

13.0 

10.7 

9-5 

8.8 

8-3 

22 

13-3 

10.9 

9-7 

8.9 

8-4 

23 

13-7 

ii.  i 

9.8 

8-5 

24 

14.0 

"•3 

IO.O 

9-2 

86 

25 

14-3 

11.6 

10.2 

9-3 

8.8 

26 

14.7 

1  1.8 

10.3 

95 

8-9 

11 

15.0 
15-3 

12.0 
12.2 

10.5 
10.7 

96 
9-7 

9.0 

29 

15-7 

12.5 

10.8 

9-9 

9.2 

30 

16.0 

12.7 

11.  0 

IO.O 

9-3 

31 

16.3 

12.9 

II.  2 

10.  1 

9-4 

32 

16.7 

II.3 

10.3 

9-5 

33 

17.0 

13.3 

II.5 

10.4 

96 

34 

s 

17-3 
17-7 
18.0 

I3.6 
138 
I4.O 

11.7 

11.8 

12.0 

10.5 

10.7 
10.8 

9-7 
9-9 

IO.O 

37 

18.3 

14.2 

12.2 

10.9 

10.  1 

38 

18.7 

14.4 

12.3 

ii.  i 

10.2 

39 

19.0 

14.7 

12.5 

II.  2 

10.3 

4o 

19-3 

14-9 

12.7 

n-3 

10-4 

19.7 

I5.I 

12.8 

ii  5 

10-5 

42 

20.0 

13.0 

11.6 

10.6 

43 

20.3 

15.6 

13.2 

11.7 

10.7 

44 

20.7 

15-8 

13.3 

11.9 

10.8 

3 

21.0 
21.3 

16.0 
16.1 

13-5 
13-7 

12.0 
I2.I 

II.O 

ii.  i 

I   tO  I 

I  tO  2 

i  to  3 

i  to  4 

i  to  5 

Cement  

500 

333 

250 

200 

167 

f\f\f\ 

750 

800 

500 

33 

INDEX 


PAGE 

Adulteration,  detection  of— in  Portland  cement 478 

Accelerated  tests  for  soundness 456 

value  of  the — 474 

Activity,  index  of— 33 

Air  separators 152 

Air  used  in  burning  cement 195 

Alit 20 

Alkalies,  influence  of— on  the  properties  of  Portland  cement 39 

loss  of— in  burning 177 

method  of  determining — in  Portland  cement,  etc 300 

Alkali-waste,  composition  of— 65 

use  of— in  Portland  cement  manufacture 64 

Alumina,  influence  of— or  the  properties  of  Portland  cement 33, 

determination  of— in  Portland  cement 254,256 

cement  mixture 329- 

rock 331 

clay 339- 

limestone '.  331 

marl 331 

shale 339 

slurry 329- 

Analyses  of  American  Portland  cements,  table  of— 29. 

coal  for  burning  cement,  table  of— 204 

natural-gas  for  burning  cement,  table  of— 218- 

raw  materials  for  the  manufacture  of  Portland  cement,  table  of —    ....  55 
Analysis  of  Portland  cement,  method  for  calculating  the  probable— from  the  mixture    91 

cement  mixture,  methods  for— 252 

rock,  methods  for— 331 

clay,  methods  for — 338 

gypsum,  methods  for — 345 

limestone,  methods  for — 331 

marl,  methods  for .  .  331 

plaster  of  Paris,  methods  for — 345 

Portland  cement,  methods  for — 252 

shale,  methods  for — 338 

slurry,  methods  for — 252 

Analytical  methods .  . 252 

Ash  of  the  fuel,  contamination  of  the  cement  by— 178 

Aspdin,  Joseph 6 

Atomic  weights,  table  of  the  more  important — 497 

Automatic  scales  for  proportioning  the  raw  materials 107 

Balance  for  testing  fineness 388 

Ball  mill 130 

Ball  test  for  consistency 412 

Ball-tube  mill  ' 139 

Bartlett  &  Snow  dryer 208 

Bates  system  for  packing  cement .  229 

valve  bag 229 


504  INDEX 

PAGE 

Baushinger's  calipers 465 

Belit 21 

Blount's  vacuum  sampler 357 

Bohm£  hammer 45* 

Boiler  for  soundness  tests 458 

Boiling  test  for  soundness 464 

Bramwell's  improved  vicat  needle 411 

British  specifications  for  tensile  strength 431 

Briquettes,  forms  of — 426,  432 

marking 438 

molding 428,  448,  450 

storage 429.  437 

Burning  Portland  cement 160 

air  used  in — 195 

chemical  changes  undergone  in — 176 

degree  of— 187 

experimental  kilns  for  trial— 493 

temperature  of— 184 

thermo-chemistry  of— 188 

utilization  of  waste  heat  in— 197 

Cage  disintegrator 211 

Calcium  carbonate,  methods  for  rapid  determination  of — in  cement  mixture 313 

Calcium  chloride,  effect  of — on  setting  time  ....       420 

test  for  soundness 465 

Calcium  sulphide,  determination  of— in  cement    , 284 

Campbell's  experiments  on  burning 185 

Capacity  of  grinders 155 

rotary  kilns 175 

Carbon  Dioxide,  influence  of — on  the  properties  of  Portland  cement 41 

determination  of— in  cement , 288,  296 

Celit 21 

Cement,  calculation  of  probable  composition  of— 91 

method  for  analysis  of— 252 

testing 348 

Cement  mixture,  methods  of  analysis 305 

proportioning 69 

sampling 305 

Cement-rock 48 

composition  of — •   • 50,  55 

methods  for  analysis  of— 331,  334,  335 

prospecting  deposits  of — 489 

Chemical  changes  undergone  in  burning 176 

Clay 53 

composition  of — 55 

methods  for  analysis  of— 338 

prospecting  deposits  of— 489 

Clinker,  cooling  of — 119 

grinding  of—  •  •  • 224 

seasoning  of — 222 

storage  of— 222 

Clips '. 430.  446 

Coal  burning  apparatus 200 


INDEX  505 

PAGE 

Coal  dryers 205 

efficiency  of  various— pulverizers 212 

powdering— -f~*~~~-r-?'.  . 210 

storage  of— 213 

analysis  of— for  use  in  burning  (table) 204 

Constancy  of  volume,  see  soundness. 

Composition  of  Portland  cement 17 

Consumption  of  Portland  cement  in  the  United  States 15 

natural  cement  in  the  United  States 9 

Conveyors 158 

Cooling  clinker,  methods  for— 219 

Cost  of  Portland  cement  manufacture 247 

plants 347 

Cracks  in  soundness  test  pats 460 

Crushers,  gyratory 121 

Pot 125 

Crushing  rolls 124 

Cummer  dryer 209 

Cylpebs  for  tube  mill 140 

Day  and  Shepherd's  investigations  on  the  composition  of  Portland  cement 22 

Degree  of  burning 187 

Description  of  Portland  cement  plants 236 

Dietsch  kiln 163 

Discovery  of  cement-rock  in  the  United  States 7 

Dome  kilns 160 

Dredge  for  excavating  marl 99 

Dryers,  for  coal 205 

stone,  clay,  etc 108 

Drying  the  raw  materials 108 

Dry  pan 129 

Dunn's  apparatus  for  burning  powdered  coal     203 

Edge  runner  mills 129 

Emerick  air  separator 152 

Equipment  of  Portland  cement  plants 239 

bibliography  of — 245 

Erz  cement 37 

Essential  elements  of  Portland  cement 43 

Excavating  marl 98 

Excess  air  used  in  burning 195 

Expansion  of  cement,  measurement  of— 465 

Factors  for  analysis,  table  of— 497 

Faija's  mixer 341 

test  for  soundness 462 

Fairbank's  automatic  cement  testing  machine 439 

Felet 21 

Ferric  oxide,  determination  of— in  cement 271,277 

mix 329 

rock 331 

day 339,344 

limestone     331 

marl 331 

shale 339,  344 

slurry 329 

influence  of — on  the  properties  of  Portland  cement 34 


506  INDEX 


PAGE 

Fineness,  balance  for — •       388 

errors  in  sieves  used  for  determining — 387 

influence  of — on  color 397 

properties  of  Portland  cement 396 

setting  time 399 

soundness 397 

strength       401 

mechanical  shaker  for  use  in  determining— 389 

methods  of  test 336,  388 

observations  on— 396 

of  raw  materials 156 

specifications  for —      386 

Fixed  lime  standard  of  control 78 

Flour  in  cement,  method  for  determining 390 

Formulas  for  calculating  proportions  of  the  raw  materials 80 

Free  lime,  microscopic  test  for — in  cement,     468 

see  soundness. 

Fresenius' tests  for  adulteration  of  Portland  cement     . 478 

Fuel  consumption  of  rotary  kilns 175 

Fuller-L,ehigh  mill 142 

Furnace  for  experimental  burnings 493 

Gano's  sampling  rod 356 

Gary-L,indner  apparatus 395 

German  specifications  for  soundness 461 

Gilmore's  needles 409 

Gooch  crucible 265 

Graphic  methods  for  calculating  proportions  of  cement  mixture 73 

Griffiu-Goreham  flourometer 393 

Griffin  mill ' .* 145 

Grinding  machinery 120 

systems  used  for  clinker 224 

raw  materials 120 

Gypsum 65 

composition  of — 66 

methods  of  analysis 345 

use  of — in  cement  manufacture .   . 223 

Gyratory  crushers ....    121 

Hammer  mill 127 

Heat  losses  of  rotary  kilns 188 

constants  for  calculating 191 

History  of  the  development  of  the  Portland  cement  industry 4 

Hoffman  ring  kiln     162 

Huntington  mill 148 

Hydraulic  index     31 

Hydrochloric  acid,  specific  gravity  of 316 

Index,  hydraulic 31 

of  activity 33 

Introduction i 

Inspection  of  cement,  methods  for — 349 

specifications  for —     348 

Invention  of  Portland  cement 6 

Investigation  of  materials  for  the  manufacture  of  Portland  cement 485 

Iron  oxide,  see  ferric  oxide 

Jackson's  apparatus  for  the  determination  of   sulphates 281 

specific  gravity 369. 


INDEX  5°7 

PAGE 

Johnston  kiln l6x 

Kent  mill J5<> 

Kilns  for  experimental  burnings 493 

forms  of — used  in  Portland  cement  manufacture 160 

Kiln  test  for  soundness 463 

Kominuter *35 

LeChatelier's  apparatus  for  specific  gravity 362 

calipers 466 

test  for  adulteration  in  Portland  cement 481 

theories  as  to  the  composition  of  Portland  cement 18 

Lenix  drive  for  tube  mills 141 

Lime,  determination  of— in  cement 255,  256,  266,  270 

cement  mixture 313,  325,  326,  329 

rock 333,  335 

clay 340.  344 

limestone 333.  335 

marl 333,  335 

shale 340,  344 

slurry 313,  325,  326,  329 

influence  of — on  the  properties  of .  Portland  cement 30 

ratio 31 

table  for  saving  calculations  in  rapid  volumetric  determination  of— 498 

Limes,  varieties  of — i 

composition  of — 3 

Limestone 44 

composition  of— 55 

methods  for  analysis  of— 331,334-335 

prospecting  deposits  of — 485 

Linings  for  rotary  kilns 172 

Load,  rate  of  application  in  tensile  strength  tests 430,  445 

Loss  on  ignition,  method  for  determining 287 

Magnesia,  determination  of— in  cement 255,  257 

cement  mix 330 

rock 333,335 

clay ?4o 

limestone 333,  335 

marl 333,335 

shale 340 

slurry 330 

influence  of— on  the  properties  of  Portland  cement 37 

specification  as  to— 39 

table  for  converting  Mg2P2O7  to—  .   .          498 

Magnesian  cement,  analysis  and  tests  of— ....     38 

Manganese,  methods  for  determination  of— in  cement 303 

Manufacture  of  Portland  cement 43 

Marl 51 

composition  ol — 55 

methods  for  analysis  of — 331,334,335 

prospecting  deposits  of— 490 

Matcham's  coal  dryer 207 

natural  draft  system  of  burning  powdered  coal 203 

Maxecon  mill 150 

Meade's  improved  Le  Chatelier  specific  gravity  apparatus 364 

multituhular  dryer 205 

Mechanical  equipment  of  Portland  cement  plants 236 


508  INDEX 


PAGE 

Methods  of  analysis  .   .   .  .   : 252 

testing 358 

Microscopic  test  for  adulteration  in  Portland  cement 483 

free  lime 468 

Mill  inspection  of  cement 349 

Mixing  mortar  for  tests 428,  435,  448 

machines  for 448 

the  raw  materials 101 

Moist  closet 407 

Molding  briquettes  for  tensile  strength  tests 428,  448,  450 

machines  for 450 

Molds,  briquette 427,  333 

Mortar  materials,  classification  of— i 

composition  of— 3 

development  of— 5 

Natural  draft  system  of  burning  powdered  coal    .  .   .  . 203 

cement i 

composition  of — 3 

production  of —    .   .   .  .   , 9 

Natural  gas,  analysis  of — 218 

use  of  for  burning  cement 215 

Newberry's  experiments  on  burnitg 181 

formula  for  proportioning  the  raw  materials 20 

investigations  on  the  composition  of  Portland  cement 19 

method  for  magnesia 335 

Newaygo  separator 151 

Normal  consistency 405,  412 

Olsens  automatic  cement  testing  machine 444 

Pttt  boiler 458 

Packing  cement 227 

Parker's  Roman  cement 5 

Per  capita  consumption  of  Portland  cement  in  United  States 15 

Pfeiffer's  air  separator 153 

Phosphoric  acid  determination  of  in  Portland  cement 301 

Plaster  of  Paris 2 

composition  of 3 

methods  for  analysis  of — 345 

Pot  crusher 125 

Powdered  coal 201 

apparatus  for  burning— 200 

composition  necessary 204 

drying 205 

grinding 210 

Power  plant  of  a  cement  mill 232 

transmission 233 

Potash,  see  alkalies. 

Producer  gas  for  burning 215 

Production  of  natural  cement  in  the  United  States 9 

Portland  cement  in  the  United  States 13 

Proportioning  the  raw  materials 69 

Pug  mill 99 

Pulverizing  the  clinker,  systems  for — 224 

coal,  systems  for — 210 

raw  materials,  systems  for— 124 

Pumps  for  marl  and  slurry .  100 


INDEX  5°9 


Puzzolan  cement 

composition  of— 3 

Quarrying 94 

Raw  materials  for  manufacture  of  Portland  cement 43 

classification  of — 44 

composition  of — 55 

investigation  of—        485 

feeding  into  the  kilns 17° 

proportioning 69 

relative  importance  of— 45 

valuation  of — 67 

Raymond  roller  mill *49 

Richardson's  investigations  on  composition  of  Portland  cement 21 

Riehl£  cement  testing  machine 441 

automatic  cement  tester 443 

Rise  in  temperature  during  the  setting  of  Portland  cement 415 

Rolls  for  crushing 125 

Roman  cement 2.  5 

Rosendale  cement 2,  8 

Rotary  dryer,  coal 205 

stone 108 

waste  heat 109 

Rotary  kiln 166 

capacity  of— 175 

efficiency  of— 188 

fuel  consumption  of—      175 

lining  for — 172 

mechanical  construction  of — 167 

method  of  feeding  raw  materials  into— 170 

temperature  of— 184 

speed  of  rotation 171 

utilization  of  waste  heat 197 

waste  gases  from— 195 

Ruggles-Cole's  dryer 209 

Sample,  preparation  oi— for  analysis 152 

Sampling  cement,  appliances  for— "  '  355 

standard  methods  of— 353 

raw  materials,  appliances  for— 306 

Sand,  crushed  quartz 432 

Ottawa  , 426,  432 

standard 426,  432 

Saylor,  David 10 

Schoefer  kiln     166 

Schumann  apparatus  for  specific  gravity 368 

— Candlot  apparatus  for  specific  gravity     369 

Scraper  for  cleaning  briquette  molds 434. 

Seasoning,  effect  of —on  cement 382,  421 

clinker 222 

Semi-wet  process 113 

Separator,  Emerick 153 

Newaygo 151 

Pfeiffer .   .  153 


510  INDEX 

PAGE 

Setting  time      405 

effect  of  calcium  chloride  upon— 420 

chemical  composition  upon— 30,  33,  425 

fineness  upon— 399 

slaked  lime  upon— 424 

storage  upon — 421 

sulphates  upon— 416 

temperature  upon — 414 

water  used  in  gauging  upon — 414 

factors  influencing 413 

methods  of  test 406,  409 

specifications  for — 405 

observations  on — 413 

Shaft  kilns 160 

Shale 54 

composition  of — 55 

method  for  analysis  of — 338 

prospecting  deposits  of — 489 

Shepherd,  see  Day. 

Shimer's  crucible 289 

filter  tube 286 

reductor 275 

Silica,  determination  of— in  cement 253,  256 

mix .   .  326,  328 

rock 331,  334 

day 338,  341.  344 

limestone 331,  334 

marl 331,  334 

shale 338,  341,  344 

slurry 326,  328 

influence  of — on  the  properties  of  Portland  cement 33 

Sieves  for  testing  fineness 386 

errors  in— 387 

Sieve  test,  limitation  of— 403 

Slag  for  use  in  manufacture  of  Portland  cement 63,  64 

Slurry,  methods  for  analysis  of— 305 

sampling 309 

Slurry  process 112 

pumps  .' 100 

Smeaton.  John 4 

Soda,  see  alkalies. 

Solid  solution  theory 21 

Soper's  experiments  on  burning !S2 

Soundness,  effect  of  chemical  composition  upon  — 30.  32 

fine  grinding  of  the  raw  material  upon — 472 

seasoning  upon — 47! 

sulphates  upon— .    473 

importance  of — 470 

methods  of  test 456 

specifications  for— 456 

Specifications  for  fineness 386 

magnesia 39 

setting  time '  ' 405 

soundness 456 

specific  gravity 361 


INDEX  511 

PAGE 

Specifications  for  sulphuric  acid 40 

tensile  strength 426 

uniform 358 

Specific  gravity,  effect  of  adulteration  on— 381 

burning  on — 379 

seasoning  on — *  ,    382 

method  of  test 362,  368,  369.  374,  376 

significance  of  test 362 

specifications 361 

tables  for  use  in — 365 

Standard  acid,  preparation  of — 314 

alkali,  preparation  of — 315 

bichromate,  preparation  of — 277 

sample  preparation  and  use  of— 317 

sand 426,  432 

permanganate,  preparation  of — 266,  271 

Steadman's  cage  disintegrator 211 

Steinbruch's  mixer 448 

Stock  house,  cement 226 

Stone  storage 104 

Storage  of  cement 226 


coal 


213 


raw  materials 103 

test  pieces 429,  437 

Sturtevant  ring  roll  mill 151 

Sulphur,  effect  of— on  properties  of  Portland  cement 40 

specifications  as  to— 40 

,          method  for  determination  of — 280,  283,  346 

Swindell  gas  producer 216 

Table  for  mixing  mortar 435 

titrations 267 

Temperature  of  burning 184 

Tensile  strength •   • 426 

effect  of  chemical  composition  upon— 30,  33 

grinding  upon— 4OI 

water  used  in  gauging  upon— 436 

method  of  test 426 

specifications 426 

Ternary  diagram  of  cement 24 

Testing  machines  for  tensile  strength 439 

Tests  to  be  made  of  cement > 359 

Titanium,  determination  of— in  cement 303 

Thermo-chemistry  of  burning 188 

Three-component  mix,  calculation  of — 86 

Tornebohm's  investigations  on  composition  of  Portland  cement 20 

Transportation  of  stone  to  mill 97 

Treatment  of  raw  material  at  different  mills 115 

Trial  burnings 491 

Tube  mills 136 

Unsound  cements,  high  tensile  strength  of— 451 

Unsoundness,  causes  ol — 470 

Vicat  needle 406 

Waste  heat  coolers 221 

dryers 109 

of  burning,  utilization  of— 197 


512  INDEX 


PAGE 

Water,  combined — in  Portland  cement 41 

determination  of — 288.  343,  347 

percentages  of — for  neat  pastes 436 

sand  mortars 430,  436 

Weighing  the  raw  materials 106 

Wet  pan .   . 129 

process 112 

control  ling  the  mixture  in— 88 

White  Portland  ceme.nt 35 

White's  test  for  free  lime 468 

Williams'  mill 127 


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